A PUK (PIN Unlock Key) code is required to unlock SIM cards that have become locked following three successive incorrect PIN entries. If your SIM card becomes locked, you will need to get a PUK code from AT&T to unlock your SIM card. You can obtain your phone's PUK code from AT&T in one of these ways:
To get your phone's PUK code online:
Once you receive your PUK code, you will need to enter it into your phone to set a new PIN code. Note: If you enter the wrong PUK code 10 times in a row, your SIM card will be invalidated, and you will need topurchase a new SIM Card. The phone will display the following error: "PUK blocked call operator."