Greetings, Jed, and glad you asked. First things first: when it comes to cell phones, “throttling” refers to the practice of a carrier intentionally slowing your wireless data speeds—usually because your carrier thinks you’re using too much data.

So, how much data is too much? That depends, of course. Most carriers say they’ll only throttle their heaviest data users, but stop short of setting a hard and fast limit—more on that in a moment.

And what happens if you do get throttled? Well, expect your carrier to restrict your smartphone to 2G data speeds—in other words, think the speed (or lack thereof) of an old dial-up modem. Once your next billing cycle begins, the leash will (generally) come off.

So, what are the respective throttling policies for the big four U.S. carriers? Let’s start with…

AT&T
Since October 2011, AT&T has been throttling the “top 5 percent” of its heaviest data users—but only for those users who have been grandfathered into AT&T’s old unlimited 3G plan, which is no longer available for new subscribers.

Related: Smartphone data plans compared

Since you’re on a “tiered” 2GB plan rather than an unlimited plan, Jed, you don’t need to worry about getting throttled for exceeding your 2GB monthly data limit. That said, you’ll still have to pay an extra $10 for every gigabyte you use above and beyond your 2GB data plan.

For those of you who still are on AT&T’s unlimited 3G plan, recent reports suggest you may be tagged as a “heavy” data user—and thus, subject to throttling—after using as little as 2GB of data within a billing cycle, which doesn’t leave much room for streaming music or video. Don’t like the threat of being throttled? Simple, AT&T says: just switch from an unlimited plan to one of its tiered data options.

Sprint
The last of the four big U.S. carriers with an unlimited 3G data plan swears up and down that it won’t throttle you under any circumstances, although there are some disgruntled subscribers who claim otherwise.

Keep in mind, though, that Sprint reserves the right to “deny or terminate service for any misuse or any use that adversely affects network performance.”

What constitutes misuse? Using your smartphone as a wireless modem without the proper tethering plan would probably qualify, as well as using heavy amounts of data while “roaming” on another network.

T-Mobile
Unlike AT&T and Verizon (which we’ll be getting to next), T-Mobile won’t charge you extra for exceeding your monthly data limit; instead, it’ll throttle your data to 2G speeds until your current billing cycle is up. In other words, throttling is less of a punishment for T-Mobile users than it is business as usual.

Related: Exceeded your monthly smartphone data limit? Here’s what you’ll pay

Verizon Wireless
The “Big Red” carrier claims it doesn’t throttle anyone. Instead, Verizon says, it employs “Network Optimization”—a system that uses “network intelligence” to slow down the data speeds of its heaviest users only “when necessary” rather than for the remainder of a billing cycle.

Well, “network optimization” is one way of putting it; in my book, though, deliberately slowing the data speed of a wireless user counts as “throttling,” even if it’s only done “when necessary.” So let’s just call “network optimization” what it is—”throttling”—and move on.

Anyway, Verizon may throttle any subscribers who are a) grandfathered into its old unlimited 3G smartphone plan (no, 4G LTE users won’t be affected), b) among the “top 5 percent” of data users in a month, and c) connected to a “congested cell site.”

How much data is too much? About 2GB or so, Verizon says, although that figure is subject to change. To find out if your data speeds are being slowed, you’ll need to check for a notice on your bill, or on the home page of your online Verizon account.

Hope that answer your questions, Jed. Have more? Post ’em in the comments below.

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Each of the biggest U.S. carriers has its own overage policies, and it’s pretty much a case of pick your poison.

The sole exception: Sprint, the last of the big four U.S. carriers to offer unlimited (well, more or less—more on that in a moment) 3G and 4G smartphone data.

AT&T
If you’re signed up for one of AT&T’s cheaper plans, such as the $15-a-month, 200MB Data Pro plan (which is on the way out, at least as far as new subscribers are concerned) or the upcoming, $20/month 300MB Data Plus option, AT&T will charge you for another month’s worth of data if you exceed your standard monthly allowance.

In other words, if you’re on the $15-a-month 200MB Data Pro plan and you use 201MB of data in a single billing cycle, you’ll see a $30 data charge—the standard $15 fee, plus $15 in overage—on your bill.

For AT&T’s pricier plans, including the $25 2GB Data Pro plan (which, like the old 200MB Data Pro plan, won’t be available to new customers as of January 22), or the new 3GB or 5G options (for $30 and $50 a month, respectively), expect to pay $10 for each additional GB of data you use above and beyond your monthly data cap.

Related: Smartphone data plans compared: Bargain plans becoming more and more scarce

Sprint
It may be the last bastion of unlimited 3G and 4G smartphone data among the big four U.S. carriers, but that doesn’t mean Sprint will let you go nuts with downloads on your iPhone or Android handset.

Like most carriers (such as AT&T, for example), Sprint has a clause in its wireless service agreements that gives it the option of throttling or even cutting off bandwidth hogs who “generate excessive amounts of Internet traffic.” It’s worth noting, though, that Sprint CEO Dan Hesse claims that “98-99 percent” of users will never run afoul of the carrier’s “terms and conditions.”

T-Mobile
The old “Get More” labels several of its smartphone 3G and 4G plans as “unlimited,” and they are … sort of.

Subscribers to T-Mobile’s Unlimited Plus (2GB of “high speed” data for $20 a month), Premium (5GB for $30 a month), and Ultra (10GB for $60/month) smartphone data plans can, indeed, surf as much as they like without fear of paying any overage charges.

But the devil’s in the details—and in this case, the key detail is “high speed” data.

If you’re a T-Mobile unlimited data user and you exceed your monthly allowance, you can kiss your speedy 3G or 4G data goodbye, as the carrier will “throttle” your data speed to 2G levels (think dial up-modem speed) for the rest of your billing cycle.

On the other hand, T-Mobile’s dirt-cheap, “Simple” plan, which offers 200MB of data a month for a mere $10 a month, isn’t an unlimited plan at all; instead, expect to pay 10 cents for every extra megabyte you use—or roughly double the rate of your initial 200MB data allowance.

Verizon Wireless
The biggest wireless carrier in the U.S. has one rule when it comes to data overages: $10 for every extra GB of data over your monthly limit, period.

Have more questions about your smartphone bill? Let me know!

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And while pricier 3G and 4G data plans do—on paper, anyway—offer more bang for your wireless buck, chances are you’re not using enough mobile data to reap any real benefit.

First, some news. As of Sunday, January 22, AT&T is scratching its $15-a-month, 200MB “Data Plus” plan from its list of options for new customers. (If you’re currently signed up for AT&T’s 200MB Data Plus plan, don’t worry—you can keep it, at least for the time being.)

That leaves T-Mobile as the sole, nationwide U.S. carrier with a sub-$20 monthly data plan for smartphones.

For $10 a month, you can sign up for T-Mobile’s “Simple” data plan, which offers 200MB of data per month.

(Note: T-Mobile’s big U.S. competitors also offer cheaper data plans for as little as $10, but only for so-called “feature” phones, not smartphones.)

The next cheapest smartphone data option for new customers is AT&T’s new Data Plus 300MB plan, which serves up 300MB for $20 a month.

After that, the smartphone plans from the biggest U.S. carriers, including AT&T, Sprint, T-Mobile, and Verizon Wireless go up and up.

Verizon’s cheapest smartphone data plan, for example, goes for $30 a month for 2GB, while Sprint—the last big U.S. carrier with a truly unlimited data plan for smartphones—offers nothing but unlimited data bundles, starting at $80 a month (including a $10-a-month “premium data” fee) for all-you-can-eat data, 450 voice minutes, and unlimited text messages.

Click chart to expand

Of course, the pricier the data plan, the more bang you get for your wireless buck—well, theoretically, anyway.

Related: How big is a GB, anyway?

Indeed, one of the worst values among the smartphone data plans in my little survey is among the cheapest: AT&T’s soon-to-expire, $15-a-month Data Plus 200MB, which comes out to a relatively hefty 7.5 cents per megabyte.

AT&T’s new Data Plus 300MB plan offers a slightly better value at 6.6 cents a MB, but that’s more than a cent and a half per megabyte higher than T-Mobile’s competing $10-a-month, 200MB “Simple” data plan.

And the more you spend, the better the value. AT&T’s Data Pro 5GB plan offers 5GB of monthly data, plus the ability to use your smartphone as a mobile Wi-Fi hotspot (more on that in a moment), for $50—or a cent per megabyte.

Up the ante even more, and the value gets better. Take Verizon’s $80-a-month 10GB data bundle, which comes out to 0.8 cents a megabyte, or T-Mobile’s “Unlimited Ultra” plan, which delivers 10GB of “high speed” data for $60 a month, or just 0.6 cents per MB.

But here’s the thing: getting great value per MB on a 10GB, 5GB, or even 2GB monthly data plan doesn’t mean much if you’re not using all your monthly data.

And according to a Consumer Reports survey from last summer, most of us don’t even come close.

Related: Which data plan should I get for my iPhone?

In fact, the survey found that the average smartphone user on AT&T consumed only about 360 MB of data a month. And when considering only “median” smartphone data use (or the largest group of users in the middle of the range), the figure for monthly AT&T data usage fell to a mere 120 MB, well shy of the 3GB data cap on AT&T’s new $30-a-month, 3GB Data Pro plan.

That’s why it’s worth checking your monthly bill or calling your carrier to see just how much data you’re using on your smartphone each month.

Are you using less than 300MB or 200MB of wireless data a month? If so, you might be better off with a cheaper data plan, even if it doesn’t offer the same value per MB as a pricier option. And if you’re using 2GB or more data a month, then hey—time to cash in on the values offered by pricier data plans.

The good news is that most carriers will let you change your monthly data plan even if you’re still under contract; the bad news, though, is that you might not have many bargain options, particularly if you’ve signed up with Sprint or Verizon.

There’s yet another key variable to consider when it comes to picking a smartphone plan: overage charges, which you can read about right here.

Got smartphone questions? Post ’em below!

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The cheapest 16GB iPhone 4S costs a whopping $649, or a full $450 more than a carrier-locked version.

Meanwhile, the 32GB iPhone 4S goes for $749 (versus $299 with a two-year carrier contract), while the 64GB model sells for $849 (compared to $399 through a carrier). Ouch.

Now, Apple is billing the iPhone 4S as a “world phone” that works on worldwide GSM and CDMA networks.

But on its website, Apple specifies that the unlocked iPhone 4S will not work on CDMA carriers like Sprint or Verizon Wireless.

Related: Why the “unlocked” version of the iPhone 4S won’t work on Sprint or Verizon

The restriction also applies to pre-paid carriers Boost Mobile and Virgin Mobile, which both operate on CDMA networks.

Standard SIM card and the iPhone 4S's smaller micro-SIM, compared

To hop from one carrier to another using the unlocked iPhone, you’ll need a micro-SIM card: a little plastic module that identifies a phone on a given carrier’s network.

You can typically request a micro-SIM card for a nominal fee (as in a few bucks or so) from the GSM carrier of your choice, although you’ll need a data plan (either pre-paid or post-paid) to go with it.

While you can buy an iPhone 4S from a carrier for hundreds less than the unlocked version, you’ll have to sign a two-year service contract to do so.

Also, the handset will be “locked” to the network of the carrier you bought it from, meaning you won’t be able to swap micro-SIM cards to jump from one network to another.

Got questions about the unlocked iPhone—or about unlocked phones in general? Post ’em below.

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According to a note posted on its online store, Apple will offer an “unlocked” iPhone 4S—that is, a version of the new iPhone that hasn’t been “locked” to a particular carrier’s wireless network—starting in November. Update (11/11/11): The unlocked iPhone 4S is now available on Apple’s website.

It won’t be cheap, though, nor will it work on Sprint or Verizon Wireless.

Expect to pay a whopping $649 for the 16GB version—an eye-popping $550 premium over an iPhone that’s “locked” for use on AT&T, Sprint, or Verizon. The 32GB unlocked iPhone, meanwhile, will go for $749, while the unlocked 64GB iPhone will sell for $849.

Looking for more of a bargain—relatively speaking, anyway? Consider an unlocked 8GB version of last year’s iPhone 4, which Apple is selling for $549.

Why the sky-high price tags? Well, the unlocked iPhone 4S is a no-contract phone that isn’t “locked” to any one carrier—meaning, unfortunately, that you won’t be eligible for any carrier price breaks.

The $199, $299, and $399 iPhone 4S models on sale through AT&T and Verizon come with mandatory two-year contracts, along with generous carrier subsidies to sweeten the pill.

The beauty of an unlocked phone (get the scoop on what “unlocked” means right here) is that you can simply pick one up, insert a working SIM card (or a smaller “micro-SIM” card, in the case of the iPhone 4 and 4S), and start making calls—perfect for those who want to use an iPhone with a non-iPhone carrier (like T-Mobile), or jetsetters who want to use cheap, local SIM cards while making calls abroad.

Standard SIM card and the iPhone 4's smaller micro-SIM, compared

What’s the catch? Well, Sprint and Verizon both run CDMA networks, which are incompatible with GSM networks and don’t even use SIM cards. Indeed, any phone used on Sprint or Verizon must be specifically programmed to work on their respective networks.

Now, the new iPhone 4S is a “world phone” that’s compatible with both CDMA and GSM networks—so, theoretically, you could call Sprint or Verizon and ask them to activate your unlocked iPhone on one of their respective networks.

On its website, however, Apple explicitly states that “the unlocked iPhone 4 or iPhone 4S will not work with CDMA-based carriers such as Verizon Wireless or Sprint.”

The restriction probably also applies to Boost Mobile or Virgin Mobile, two pre-paid carriers that also employ CDMA networks.

In any case, you can always snag a pre-paid micro-SIM card from AT&T, T-Mobile, or any number of other pre-paid carriers carriers (they’re available for a buck and up on Amazon), plug it into your new unlocked iPhone, and start chatting away.

A couple of quick caveats about using 3G data on an unlocked iPhone:

• You’ll need a data plan associated with your micro-SIM card to surf the web, stream music, or otherwise consume cellular data on an unlocked iPhone. If you’re using a post-paid micro-SIM card and you start surfing away without a data plan, you may get hit with exorbitant data fees, so easy does it. Another option: skip the data plan and only use Wi-Fi data. To do this, tap Settings, General, Network, and then flip the Cellular Data switch to Off.
• While you can access data on T-Mobile’s network through an unlocked iPhone, the iPhone 4 doesn’t support the proper frequencies for T-Mobile’s speedy 3G and 4G networks. That means you’ll have to settle for the slower EDGE network, which is OK for email and light web surfing but a non-starter for streaming music or video.

Got more questions about the unlocked iPhone 4S? Sure you do. Leave ’em below, or shoot me an email.

Note: I’ve updated this story to include information and pricing for the new, unlocked iPhone 4S and the older iPhone 4. 

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Naturally, the crush of callers following Tuesday’s scary earthquake here on the East Coast soon jammed the airwaves, leading AT&T, Sprint and T-Mobile to urge subscribers to text, e-mail, or tweet their friends and family—just please, don’t call.

“Call delays due to temporary mass calling event,” Sprint said on its official Twitter feed. (“Mass calling event?” Nice one.) “To contact loved ones following earthquake, please use text mesgs rather than call.”

T-Mobile had the same much the same advice on its own Twitter feed, reporting that its network was “experiencing higher call volumes in all areas affected by the earthquake.”

AT&T users (myself included) also had trouble making connections, while Verizon Wireless owned up to “some network congestion” following the 5.8 (or 5.9, depending who you talk to) temblor.

But scared East Coasters who had the good sense to hang up their phones and turn to Facebook, Twitter, or good old-fashioned texting had much better luck getting through to their loved ones.

Moral of the story? When the earth shakes beneath your feet, resist the urge to call home and try texting, posting, or otherwise tapping instead.

Did you feel the quake—and if so, were you able to get in touch?

Update: Even the Department of Homeland Security now says you should stick to Facebook and Twitter when it comes to contacting loved ones about the quake:

If White House town hall meetings via Twitter and Facebook weren’t proof enough that we’re moving well into the Gov 2.0 era here in the US, then this might help sway your opinion. The Department of Homeland Security, seeing massively clogged telephone connections on the East cosat following a Virginia earthquake, is encouraging the use of social media to contact friends and family.

via The Next Web

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That’s bad news for those of us who don’t send and receive, say, 100 messages a day, and based on a quick survey of the post-paid messaging plans offered by the other big carriers, unlimited messaging plans are increasingly becoming the norm rather than the exception.

In other words, the days of getting monthly “buckets” of, say, 200 or 500 messages seem to be numbered.

The scoop on AT&T’s “streamlining” of its messaging plans comes from Engadget, which confirmed the news with AT&T and adds that the changes will take effect August 21.

AT&T also promises that current customers will get to keep their existing messaging plans (including the soon-to-be-extinct $10-a-month plan for 1,000 messages), even if they decide to change phones.

The other big carriers also seem eager to sign us all up for unlimited text/picture messaging plans, while at the same time weaning us off unlimited data for our smartphones.

So, what exactly are our messaging options for the big four U.S. carriers: AT&T, Sprint, T-Mobile, and Verizon Wireless?

I surfed around the various carrier sites and culled a few facts and figures, with the chart below taking AT&T’s upcoming plan changes.

First of all, check out the prices for paying per message. Twenty cents each, both to send and receive? Yikes—and that’s just for text messages, with AT&T charging as much as 30 cents per picture message.

Also, limited buckets of messages are becoming increasingly scarce. AT&T and T-Mobile don’t offer them at all, while Sprint and Verizon only offer a couple buckets each. (Verizon Wireless’s $20-a-month, 5,000-message bucket is intended for those on family plans, by the way, while individual lines can get unlimited messaging for the same price.)

The biggest bargain? T-Mobile’s $10-a-month unlimited messaging plan for individuals. Verizon Wireless, on the other hand, will only give you 500 messages for $10 a month.

While Sprint and T-Mobile will sell your separate individual and family messaging plans, they’re also seriously hyping their unlimited bundles (which include different combinations of voice, data, and messaging), with each carrier offering bundled unlimited plans starting at $49 a month.

Overall? Like it or not, the big carriers seem to be pushing us all toward unlimited messaging plans—and hey, that’s great for those who send thousands of SMS messages a month, but it’s not so wonderful for anyone (like me, frankly) who only needs to fire off a text or two a day.

So, what about you? Do you have an unlimited messaging plan or a bucket of messages—or do you pay per message?

(Photo credit: iStockPhoto)

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Unless you’re on Sprint, there’s a good chance your cell phone carrier has you on a short leash when it comes to speedy wireless data.

Indeed, most carriers now limit, or “cap,” their 3G and 4G data plans at levels ranging from 200 MB to 10 GB a month, and they’ll charge you extra if your creep over your monthly limit. (Not sure how big a megabyte or a gigabyte is? Click here for help.)

But here’s the thing: according to a recent Consumer Reports survey, you might actually be using a lot less smartphone data than you think—and that means you may be paying more on your data plan than you need to be.

Indeed, the survey found that the average smartphone user on, say, AT&T, used only about 360 MB of data a month—a figure that’s skewed by a “small percentage” of data hogs downloading huge amounts of data onto their phones.

When considering only “median” smartphone data use (that is, the largest group of users smack in the middle of the range), the figure for monthly AT&T data usage falls to a mere 120 MB.

That means the typical AT&T subscriber could safely downgrade to the carrier’s $15, 200 MB-a-month “DataPlus” plan with room to spare.

The median Verizon Wireless smartphone user consumed slightly more data than those on AT&T—think 158 MB a month rather than 120 MB, according to Consumer Reports. Meanwhile, median data use on T-Mobile was a mere 48 MB a month.

Surprised? I certainly was, although I figured that my own smartphone data use was probably somewhat above the mean.

Well … turned out I was only half-right. Logging into my account over the AT&T web site, I found that I’d used less than 100 MB of data a month for February and March, and just a little more than 200 MB each in April and May. In June, my iPhone 3G data use slipped to about 150 MB, although it skyrocketed to a whopping 923 MB in July—but only because I’d been performing a little 3G battery-drain test.

So, what does all this mean to you? Well, consider checking with your carrier to see how much wireless data you’re really using each month. You can log into your account online, or just call and check with customer service.

Once you’ve figured out how much data you’re using each month, check out your carrier’s data-plan options.

Using less than 200 MB of data a month? Maybe you should switch to a cheaper 200 MB smartphone plan, provided your carrier offers one. (AT&T and T-Mobile do, for $15 and $10 a month, respectively; Sprint and Verizon don’t; check out this post for more details.)

Source: Consumer Reports

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The Motorola Photon 4G (available from Sprint on Sunday, July 31, $199 with a two-year contract) boasts many of the same features as its bleeding-edge Android competitors, including a huge, razor-sharp display, dual cameras (including one for video chat), and a super-fast, dual-core processor (meaning two processors on a single chip, good for speedier and more efficient performance).

What sets the Photon 4G apart, though, is its optional, $99 multimedia dock accessory, which comes with an HDMI video output and a trio of USB ports. (A similar dock is available for the Motorola-made Atrix 4G, available on AT&T.)

The dock’s video outlet lets you connect the Photon 4G to any HDMI-enabled HDTV or computer monitor, while the USB ports will easily handle a mouse and a keyboard. (The Photon is also capable of connecting to a wireless Bluetooth keyboard, which Sprint will sell you for an extra $69.)

Once you connect the so-called “HD Station” dock to a nearby HDTV—say, the one in your hotel room—and slide the Photon 4G into its cradle, the phone will give you the option of doing something pretty neat: turning your big-screen TV into a computer desktop, complete with a PC-caliber web browser.

Now, just to be clear, don’t expect your smartphone-powered HDTV to suddenly start running Microsoft Word and Photoshop. Indeed, the only PC-level application you’ll find on the Photon 4G is a custom version of the Firefox web browser—which is probably why Motorola named the Photon’s PC-on-a-TV application “WebTop” rather than, say, “PC Desktop.”

I should also note that the Photon 4G’s Firefox browser managed to surf the web at a steady, if not lightning-fast pace, while opening too many windows at once triggered a “low memory” alert.

Then again, you could do things like play Flash videos on the full YouTube website, or edit documents, presentations, and spreadsheets in Google Docs—in fact, I wrote most of this post in Google Docs using the Photon 4G’s Firefox browser.

And if you want to dive into regular smartphone apps, you can always do so using a windowed or full-screen “Mobile View” app.

So while the Photon 4G and its HD Station dock certainly don’t qualify as a PC-replacing duo, they could do the trick for a hotel-bound business traveller looking to catch up on email or spruce up a report—and all you’d need in your suitcase would be the Photon’s compact dock, a travel mouse, and a portable USB keyboard.

Very nice—and given what phones like the Photon 4G can do today, just imagine where we might be in a few more years. Maybe the days of us carrying around PCs in our pockets aren’t so far off after all.

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Why? Because there are two very different flavors of cellular networks and phones in use around the globe: CDMA and GSM, and they’re about as compatible as dogs and cats.

And yes, you guessed it: AT&T and T-Mobile use one of these competing technologies, while Sprint and Verizon use the other.

Indeed, every wireless carrier in the world must choose between either CDMA (short for “code division multiple access”—yikes) or GSM (“Global System for Mobile Communications) cellular technology.

In Europe and Africa, you’ll mainly find GSM networks; in Asia, CDMA pretty much rules the roost.

Here in the U.S., we’re split more or less down the middle, with AT&T and T-Mobile using GSM, while Sprint and Verizon go the CDMA way.

OK, so what’s the biggest difference between GSM and CDMA networks?

The most obvious one is that GSM technology uses a tiny plastic card, called a “SIM” (short for “Subscriber Identification Module”), to identify a specific phone on its network.

An AT&T SIM card in an iPhone 3GS.

Plug the little SIM card from your carrier into a GSM-based phone (the SIM usually sits in a slot near the battery), and it’ll ring when someone dials your mobile number; remove it and put it into another phone, and the second handset will essentially become “your” phone.

CDMA phones, on the other hand, don’t use SIM cards. Instead, CDMA carriers (like Sprint or Verizon) must program a specific handset to work with your mobile number.

There are a series of other, often highly technical difference between CDMA and GSM (one being that CDMA phones only support a maximum of three people on a call at once, versus up to eight on a GSM phone), but here’s the bottom line: a CDMA phone won’t work on a GSM network, and GSM phones won’t work on CDMA networks.

And unfortunately, there’s one more twist.

Theoretically, you should be able to plug your AT&T SIM card into a T-Mobile phone and start making calls; that said, most carriers “lock” their phones to their respective networks.

For example, the AT&T iPhone is locked to AT&T’s network, meaning you won’t be able to use it on another GSM carrier, like T-Mobile.

Those who want an iPhone that will work on any GSM carrier will have to shell out more than $650 for an “unlocked” version of the iPhone (which is sold directly by Apple, and doesn’t come with any carrier discounts—hence the sky-high price tag).

That’s the bad news; the good news is that some GSM carriers, including T-Mobile, will unlock a phone after a certain amount of time (typically four months or so or so) has passed on your contract; all you have to do is call and ask. (Sorry, AT&T iPhone users: AT&T won’t unlock your iPhone for you, although you can always try “jailbreaking” your iPhone if you’re feeling brave.)

Have more questions about the difference between CDMA and GSM phones and networks? Let me know!

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