A subscriber identity module (SIM) card is a small chip that is used by global systems for mobile communications (GSM) cellular phones. The SIM card allows the cellular service provider to identify subscribers using the network. SIM cards are removable and you can transfer a SIM card to another GSM cellular phone. When inserting the SIM card into a new phone, you normally have to enter a PIN (Personal Identification Number) code. If you enter the PIN code incorrectly multiple times, your SIM card will lock and you will need to enter a PIN unlock code (PUK) to unblock your SIM card.
Instructions
1. Call your current cellular service provider and request the PUK code for your SIM card. You also might be able to obtain the PUK code from your account on your service provider's website.
2. Insert the SIM card into a GSM cellular phone. Your phone will prompt you to enter the PUK code.
3. Enter the PUK code using the keypad on your cellular phone. Your SIM is now unblocked.
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