FREE UNLOCK for Samsung Galaxy S3 and Note 2 Phone. Valid for GSM version like AT&T.
- 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
- 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. Now your phone is unlocked!