Default [Q] Purchased unlock code but it isn't working help!

Hey there guys I purchased an unlock code for a blacklisted i337 I have which recently was serviced by Samsung because the Wifi stopped working. Anyways I purchased an unlock code where I was given an NCk code and a freeze code but when I put in an unacceptable Sim and then put the code in it keeps saying unsuccessful. Does the phone need to be activated on at&t again before this is possible? Of course Samsung flashed the latest 4.4.2 nc1 so please any info would help