While the best unlocked phones almost certainly support GSM carriers like AT&T and T-Mobile, it’s best to look for devices that work with all the major U.S. providers, including Verizon.

For instance, if you buy an iPhone directly from Apple, the manufacturer, you could use the phone with a SIM card from AT&T, ...

And in some cases, like with Verizon, you’ll have your phone unlocked within 90 days whether it is paid over or not. You give up a lot of freedom with carrier-locked phones, both from the ...

An "unlocked" phone gives you complete freedom from carrier restrictions. You can insert a SIM card from AT&T, T-Mobile, Verizon, or any other compatible carrier and start using their service ...