I have a Pantec C820 phone from AT&T. I have the unlock code but cannot find instructions that work. Can you help me?

This is the same procudure I have tried before. I tried it again; 3 times. When I finish entering the last character, the screen/phone does nothing until I press "enter" and each time I get an "info failed" message and can go no further. This is the same procudure I have tried before. I tried it again; 3 times. When I finish entering the last character, the screen/phone does nothing until I press "enter" and each time I get an "info failed" message and can go no further.

For some unknown reason, both of the unlock instructions I have been given for this phone do NOT produce the expected screen or options to unlock it. I'm beginning to think the phone was NEVER locked by AT&T when I bought it. I put a T-Mobile SIM in it and it worked just fine on the T-Mobile network. I'm going to try it with a Verizon SIM and see what happens. For some unknown reason, both of the unlock instructions I have been given for this phone do NOT produce the expected screen or options to unlock it. I'm beginning to think the phone was NEVER locked by AT&T when I bought it. I put a T-Mobile SIM in it and it worked just fine on the T-Mobile network. I'm going to try it with a Verizon SIM and see what happens.