Can you use your existing phone if you move to AT&T?

Not that long ago, it was practically impossible for a phone from one US carrier to work on another US carrier. AT&T and T-Mobile used one technology, Verizon another, Sprint another, and other cell companies used variations on one of the top carrier’s tech.

What changed? LTE, that’s what.

Why does LTE make a difference?

LTE, in case you were ever curious, stands for the “Long Term Evolution of the GSM standard.” OK, what’s GSM, I can hear you ask. GSM is the standard developed by the European “Groupe Spécial Mobile” in the 1980s. It became the standard for digital cell phones in the 1990s in Europe, and was adopted as well by Cingular (now AT&T) in the 2000s. All Cingular and AT&T phones were GSM phones, while Verizon and its predecessors used CDMA technology which was more common in Asia at the time. Sprint stuck it out throughout the 2000s with a version of the TDMA technology abandoned by Cingular. It seems Sprint has always been just a little bit behind.

GSM was at its heart a voice protocol. It was the one of the first standards that was designed for text messaging, but it really wasn’t designed for data. Today of course we use our phones mostly for data.

LTE was created in order to bring GSM into the next generation of data services. The latest version of LTE is already bringing data speeds of close to 100 megabits per second to the latest generation of cell phones. No other cell standard even comes close.

If you want high speeds, you want LTE.

And, if you want LTE, you have to basically take parts of the GSM standard as well. LTE is based on GSM so they’re sort of inseparable.

That’s a good thing because it means that if you have nearly any high-end phone you can bring it to AT&T and it will work. Even phones from Sprint must have the hardware needed to run on an LTE network.

Essentially, any late model iPhone or Galaxy will work on the AT&T network in some way or another. There are two things, however, that you might need to consider.

Carrier locking

Some phones are carrier locked. This was much more common five years ago in the era of the free phone. Today most phones are not carrier locked. Carrier locking involves putting special software into the phone that makes it work only on one network. Sometimes this software is built deep into the phone’s hardware. Most carriers will unlock a phone for you for free if you truly own it. By law they have to, although some will give you a hard time.

Here’s how you can tell if you’re carrier-locked. First, factory-reset your phone, Look at what’s installed. If it still has apps with the name of your carrier (Verizon, T-Mobile, Sprint) that you can’t delete, it’s probably carrier locked.

Data speeds may vary

Not every phone is capable of receiving every frequency. Pretty much every phone will receive voice frequencies from all carriers, but when it comes to data they can vary. You may get 3G speed but not 4G or LTE speed if your phone can’t receive the frequencies needed. You can generally look at the manufacturer’s web site to see which cellular bands are available to any specific phone. From there, use a tutorial like this one to figure out if your phone will receive all the bands you’ll need.

As a general rule…

Because all phones today support LTE, nearly all of them will work out of the box if you want to bring them to the AT&T network. However, you may find that you don’t get the best performance out of them. If you activate a phone with AT&T, there are generally steps you can take if it’s not giving you the speed you want. You can upgrade the phone. Some states also allow you to end your relationship with a carrier at no charge. The time to do that is usually fairly shortly after you activate.

About the Author

Stuart Sweet
Stuart Sweet is the editor-in-chief of The Solid Signal Blog and a "master plumber" at Signal Group, LLC. He is the author of over 8,000 articles and longform tutorials including many posted here. Reach him by clicking on "Contact the Editor" at the bottom of this page.