PUK means Pin Unlock Key and it is required to unlock Pin when Pin is entered 3-10 times incorrectly. PUK is saved on the SIM card. You need to contact your service provider to get the PUK (simply dial their customer care number and listen to and follow the voice prompts). Note: If you enter the wrong PUK code 10 times in a row, your SIM card will be invalidated, and you will need to purchase a new SIM Card. The phone will display the following error: PUK blocked call operator.