iPhone SIM card is locked

If your SIM card is locked and asking for a PIN code, then contact the carrier for that code. You will not want to guess, as if you enter the wrong code too many times it will ask for a PUK code. If the wrong PUK code is entered too many times it will require you to purchase a new SIM card.

There is only one solution and that is to contact the carrier the phone is locked to and see if the phone qualifies to be unlocked and what if any costs might be required to be paid for them to unlock the phone. No one but the carrier can unlock the phone.