Thanks to the Unlocking Consumer Choice and Mobile Unlock, it’s perfectly legal to unlock your phone and switch to a new carrier.

Unlocking your phone is legal, but some restrictions, as they say, may apply. Your phone needs to be fully paid for, whether you have a completed installment plan or come to the end of a two-year contract. If you have a prepaid phone, carriers can’t lock you in for more than 12 months.

In addition, the phone you seek to unlock must not be reported lost or stolen and your account must be in good standing.

We’ll cover how the big four carriers in the U.S. — AT&T, Sprint, T-Mobile and Verizon — handle unlock requests. Before we get to the carriers, however, you should check to see if your phone is locked.