PIN and PUK numbers
Some pre-paid SIM cards have a safety device set up that needs the user to enter in a Flag (Personal Identification Number) code everytime the phone is turned on. Each time a Flag code has been given it’s essential never to overlook this code. Should you enter the PIN code incorrectly to the phone 3 times in a row then your phone will exhibit a ‘Blocked’ information. When this occurs you will then be required to unblock your telephone using the PUK (Personal Unblocking Key).
If you enter the PUK wrongly 10 instances in a line you will block your SIM card forever and you will have to purchase a new one. Every handset might have a distinct set of procedures so you might have to consult your telephone manual for complete details to allow PIN locks.