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 unauthorized 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 carrier can provide you with the unique PUK code for your device. Warnings Writer Bio
