If you forget the PIN of your Apple iPhone 4S and enter the wrong PIN more than three times, then the SIM card gets locked. PUK code comes into work then. You can only unlock Apple iPhone 4S using the PUK code. This PUK code is received from the customer care. You can make a call to the customer care from a Three phone which is toll free, and it will charge you the standard rate if the call is made from any other phone. The rate is 5p per minute for BT line, and it varies for other networks.
Way to unlock Apple iPhone 4S using the PUK code
When the SIM card is locked because of various attempts by the wrong PIN, a windows is visible on the screen by showing a message that ‘Your SIM can’t be accessed and call to the carrier to obtain PUK code with two options OK and Unlock.
The next job is to call to the customer care. The number is 333 or 0333 000 3333 for Three phone and other phones. You can obtain the PUK code from them. Be sure that you have collected the right PUK code.
> First press the Unlock option on the screen.
> You will be then asked to enter the PUK code. Enter the correct PUK code as incorrect PUK code will block the SIM permanently, and you will lose all the data stored on the SIM. And the only way to get back the SIM is by getting a new SIM card.
> Enter a new PIN as per your choice.
> Again insert the PIN and press ‘OK’.
> Your SIM card will be unlocked.
So this is the full process to unlock Apple iPhone 4S using the PUK code.