What should I do if the phone is asking me to enter a PUK code?

After three consecutive incorrect SIM card PIN code entries, the code is blocked, and you need the PUK code to unblock it. Contact your service provider.
After ten consecutive incorrect PUK code entries the SIM card will be permanently disabled. If you disable the SIM card following the incorrect input of the PUK code, you will need to contact the service provider to buy a new SIM card.