Can I use an AT&T SIM in a T-Mobile phone?

With carrier seemingly offering shorter and shorter contracts all the time, it's easier than ever to bounce around and find the one that suits you the best. But, you don't necessarily want to have to get a brand new phone every time you change carriers.

If you're moving from T-Mobile to AT&T, there's a few things you need to double-check before jumping ship.

Is your T-Mobile phone unlocked?

You can't just change carriers willy-nilly, since buying a phone from them means that it's programmed specifically for that carrier and locked to their network. You can add all the APN settings you want, but it probably won't work.

First, you have to unlock your device, which (luckily) T-Mobile makes relatively easy. It all starts with requesting an unlock code from T-Mobile. From there, they'll examine your account history to see if you qualify.

They reserve the right to refuse an unlock code to anyone at any time, so make sure your bills are paid up and your account is in good standing. Android users can download the Mobile Device Unlock app so that you don't even have to talk to T-Mobile customer service.

Is your T-Mobile phone compatible with AT&T's network?

When switching carriers, you first have to make sure that your phone is compatible with the new carrier. The way to do this is to find out which radio bands AT&T uses and then make sure your phone supports them. AT&T's main band is 17, so if your T-Mobile phone supports band 17, you should have no problem with it working on AT&T's network.

The bottom line

If your phone has been unlocked from T-Mobile and is compatible with AT&T's network, then you should be able to use an AT&T SIM in a T-Mobile phone.

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