How to bring your old phone to a new carrier

Switching mobile providers can save you money, though keeping the same handset is hard to do. Hard, but not impossible.

Last updated: March 12, 2015 11:00 AM

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Lots of smart-phone customers suspect they could get a better deal by switching carriers—and they're probably right, especially if they're still on an old contract plan. You'd think the deals would be even better for consumers who bring their existing phones along with them. Now, that's not easy to do, and phones have improved so much in the past few years that it could make more sense to upgrade. However, if you committed to keeping your phone while moving to a new mobile provider, here's what you need to know.

1. You may have to pick a lock

Many AT&T and Sprint phones—and some Verizon phones—are locked to their carrier networks. That means you can’t take the phone to another carrier until you, or the new carrier, gets a special code. That should only take a few minutes if you’ve completed the terms of the contract and your account is in good standing. However, if the account with your current carrier is in arrears, you probably won't be able to do it. And even if you do get the phone unlocked, that's no guarantee that it will function with your new carrier.

2. Phones don't all work on the same networks

Deep-rooted technology differences mean that many devices won’t work on multiple carriers' networks. For instance, Sprint and Verizon use a technology loosely labeled Code Division Multiple Access (CDMA), while AT&T and T-Mobile use Global System for Mobile Communication (GSM) and Universal Mobile Telecommunications System (UMTS) technologies. These major carriers have now supplemented their third-generation (3G) networks with faster 4G LTE networks, but that hasn't solved the compatibility issues. (Generally speaking, GSM smartphones work across more of the world than do CDMA models, but many CDMA models have the hardware needed to support the frequency bands and technologies used abroad.)

Some AT&T phones may be able to roam on T-Mobile’s networks, and vice-versa. Ditto for Sprint and Verizon phones. But there's a caveat. Even if you can get calls through, there’s an excellent chance your phone won’t be able to access some cell towers, or your new carrier’s faster data networks. Fortunately, there's a sort of work-around to this problem, and it is provided by the smaller providers who increasingly are competing with the big, national carriers.

Learn how to save money on your phone plan and get the best cell phone plan for your family. And find out why small carriers outrank the big ones in our latest cell phone service survey.

3. You can switch carriers without switching networks

Here comes the good news. There are four major cellphone networks in the United States—but a lot more phone carriers. The reason is that the smaller carriers piggyback on technology built and maintained by the big players: AT&T, Sprint, T-Mobile, and Verizon. For instance, Consumer Cellular uses AT&T’s network, while upstart Ting Wireless uses Sprint’s network. The small carriers are what’s known as Mobile Virtual Network Operators (MVNOs)—and our research shows that people like them.  

If you choose a new carrier that's on the same network as the carrier you are leaving, you have reasonably good odds of getting your phone to work the way you want it to. (You can find a fairly comprehensive list of which MVNOs use which networks on Wikipedia. Of course, you can also call the new carrier and just ask whether your old phone will work.) Those odds are even better if you choose one of the upstarts, notably Ting Wireless, which offers service on Sprint's cellular network at better rates and friendlier terms.

But there are no guarantees—the world of mobile carrier business deals and technologies can be murky. For instance, a couple of years ago, Ting subscribers had to wait several months before they could bring iPhone 5 models to the carrier. As a second example, for many years the carrier Cricket used CDMA networks. But when AT&T acquired Cricket several years ago, the larger company began phasing out the old Cricket network and began a strong push to move its customers to the larger company's GSM network.

By the way, there's another compatibility issue besides the one we've been describing. The SIM card in your smart phone stores your account information and other details. When you switch to a new phone, you can remove the card from the old phone and insert it into the new one. But this can be tricky as there are different-size cards, and older cards may not work with newer carrier services.

The bottom line is that if you really want to bring a late-model phone with you to a new carrier, you may be able to. But most people will find it much more convenient to just plan on buying a new phone.

—Mike Gikas

Shopping for a new phone? Watch this video first.

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