Need to unblock card

Pin Unlock Code (PUK)
If you miss keyed (or forget) your SIM PIN code, and enter the wrong one 3-5 times in a row, the sim will lock up, and you’ll need to enter the unlock code to release it. You should ask your Network Service Provider for this code when you need it. Don’t try to guess it, because after a few wrong guesses, the SIM card will be permanently disabled.
Blacklisting:
This is not a security code, but it works like one! To help combat mobile phone thefts, the networks share a database of the IMEI (International Mobile Equipment Identity) of mobile phones that have been reported stolen. Once a phone is on this list, it will not be allowed to use any of the networks.
This can be a risk if you buy a second-hand phone, because if it has been stolen, or if an unscrupulous seller makes an insurance claim after selling, the phone you bought in good faith may be permanently disabled.
Be very careful to check the source of a second-hand phone!