Default [Q] S4 Network unlocking issues

I have been trying to unlock my AT&T S4 and after trying several methods am having no luck. I tried the *#0011# and am unable to make any changes due to an update that I can't seem to get rid of. I purchased an unlock code from a reputable unlock site, (bought one from them previously for girlfriends AT&T S4 and it worked perfectly) the code for my phone won't work. They offered several troubleshooting steps, from various *# number combinations to factory resetting my phone. I did a hard wipe (holding down vol up, menu and power button) and that still didn't work. I am thinking maybe I could try flashing an earlier version of android? Does anyone have any suggestions that I could try? Any help would be greatly appreciated. Thank You!