=====ALL Credits to Owl74 on XDA-Developers=====http://forum.xda-developers.com/s...ostcount=1
This is confirmed by myself to work on the AT&T Galaxy S3 and AT&T Galaxy Note 2 ....and it is reported to work on ALL VARIANTS of GSM.
I am posting it publicly to give where credit is due, and to KILL the ebay profits, specifically ebay Item: 321033698090
Please do not profit off someone elses' idea and ebay this info like the Joker in the auction above
To unlock your Galaxy S3 OR NOTE 2:
Just dial the following keys *#197328640#
Main Menu >  UMTS >  Debug Screen >  Phone Control >  Network Lock > Options Perso SHA256 OFF > (after choosing this option, wait about 30 seconds, then go back one step by pressing the Menu button then select Back, now you are in  Network Lock then choose  NW Lock NV Data INITIALLIZ ..... wait for a minute then reboot your phone... enjoy!!!
/standard disclaimer: I am not responsible if you don't follow directions and what you do with your phone...