The PUK code, or Personal Unblocking Key, unlocks a cellular SIM card -- it's a code for the security of your personal information and telephone line, which is stored on the card. In the case that you cannot remember your PIN number for your SIM card or have entered it incorrectly, resulting in a security lock of your SIM card, the PUK reauthorizes the SIM card. Your phone will automatically prompt you for the PUK code when it is necessary, or after three failed attempts to use your PIN number to access your SIM card. Typically you will get 10 attempts to enter the correct PUK code and restore your SIM card to its active functioning status. PUK codes are available from your cell phone service provider.
Obtain the PUK code from your cell phone service provider. Call customer service, log in to your online account to view your device settings, or review your user manual. Look for a four-digit code (or higher), and be sure to write down the PUK code for future reference.
Attempt to enter your SIM pin three times, or allow your phone to prompt you for your PUK code. Enter the exact code provided by your cellular service provider. Confirm submission of the code when prompted. Continue to try codes up to 10 times. Use "0000" as the standard PUK code for most devices.
Wait for confirmation that the code has worked. Enter a new SIM pin number when prompted. Choose a memorable four-digit combination of numbers. Note your new PIN number for your records.