You may have to reset the PIN code on your device.
An AT&T phone can be activated by simply inserting your old AT&T SIM card into the device. If the SIM card security feature is in use, however, you won't be able to use the device without unlocking the SIM. A locked SIM card will request you to enter a code, usually referred to as a SIM PIN. The PIN is four to eight digits in length. If you are unsure of the PIN, you can attempt to unlock it using the default code set by AT&T.
Instructions
1. Insert the old SIM card into the phone you intend to use it with. (Most phones house the SIM card under the battery; refer to your user guide for details.)
2. Press the phone's "Power" button to turn it on. When the device starts up, "Enter PIN" or "Enter SIM PIN" will display if your SIM card is locked.
3. Enter in the four to eight digit SIM PIN. If you are unsure of the PIN, try using AT&T's default PIN of "1111."
4. Press "OK." If you entered the correct PIN, an "Unlocked" message will display. If you receive an incorrect code error, continue to the next step.
5. Enter in the default PIN --- or attempt to guess the PIN --- until a "PIN Blocked" message displays. (After three wrong SIM PIN entries, you will see this message.)
6. Contact AT&T customer support by calling 1-800-331-0500, and request the PUK (PIN Unblocking Key) for your device. (If you have a myWireless Account registered online, see the link in the Resources section for step by step instructions for obtaining your PUK through AT&T's website.)
7. Enter the eight digit PUK using your phone's keypad and press "OK."
8. Type in a new PIN code of your choice; pick a number you will remember. The PIN should be four to eight digits in length.
9. Re-enter your new PIN code to confirm. Press "OK." If all codes were entered correctly, your SIM card will now be unlocked and ready for use.
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