If your phone uses a SIM card to operate, you can activate a security feature called a SIM PIN. The SIM PIN protects your SIM card from unauthorised use, and must be entered in order to use your phone. Enter it incorrectly three times and your SIM card becomes locked. You can unlock your SIM card on your own, however, by typing in a PIN unlock key. Your network can provide you with the unique PUK code for your device.
Contact your network provider by calling the freephone customer service number. (Find this on your provider's website or a recent bill). You will need to verify your account password before the PUK code is released to you.
Power your phone on. You will see a "SIM Locked" or "Enter PUK" message. Type in the eight-digit PUK code and press "OK."
Type in a new four to eight-digit PIN code when prompted, then press "OK."
Verify your new PIN code by re-entering it when prompted. Press "OK." Your SIM is now unlocked.
If the PUK code has been entered incorrectly 10 times, your SIM card is permanently locked. You will need a replacement SIM card.