Hi dear @wahid45105 @ you need a PUK (Personal Unblocking Key) if you enter the SIM's PIN incorrectly three times.
Usually the handset will display a message that the PIN is blocked and asking you to enter the PUK. If not, then restart your phone and try again
If you are asked for the PIN again, enter 5555 or 6666 (this is assuming you have not changed the PIN from the factory default). If asked for the PUK, enter the 8 digit number you got from giffgaff.
If you enter the PUK incorrectly 10 times, you will permanently block the SIM and will need a new one.
For further details please visit this link.