To unlock a Nokia phone, enter the PUK number and key in a new PIN. To confirm the code, re-key the PIN once more before entering the code into the handset device. The PUK allows you to access the phone if you enter the PIN for the SIM card information incorrectly and allows you to gain access to the carrier network.
The SIM, or subscriber identification module, contains your subscriber details and uses this information to gain entry into the carrier network. The Nokia and other mobile devices use the PUK, or personal unlocking key, to safeguard your SIM card information.
The mobile phone PIN usually consists of four to eight digits. If you enter the PIN incorrectly three times, the phone requests that you enter a PUK. According to Verizon Wireless, a PUK that is incorrectly entered 10 times disables the SIM card, so it must be replaced.
A default PIN is usually assigned for a SIM card. Therefore, change the PIN as soon as possible to reduce any risk to your privacy and security. Do not bend the SIM card, and keep the card dry and clean. Avoid extreme temperatures when using a Nokia or any mobile device.