[Q] Problem with unlocking LG G2 D800 topic

I purchased LG G2 D800 (32gb) locked to AT&T network. I wanted to unlock it with a code and tried various webstites - 3 of them replied that they cannot offer any support, 2 emailed me back with an unlock code. Codes from those 2 different websites were the same, however it did not work - I now have the last attempt left to unlock it. I tried through one of the 'shops' as well, but they couldn't help either. Can you please advise if you have a reliable way of unlocking or obtaining a code for unlocking? Is there any other way to unlock this phone? Maybe at least a way of bringing the count of tries back to 1? I also tried ringing AT&T but they could not help, as I did not have an account with them - I'm stuck.
Thanks for any help or suggestions you may have,