First of all, please note that the following method of unlock has been confirmed on most of US and Canadian GSM carriers, such as AT&T, T-Mobile, Bell, Rogers, Telus and etc. It’s also confirmed to work on AT&T Galaxy S3 and Note 2. It is reported to work on ALL variants of GSM.
Requirements for Samsung Galaxy S3: You need to update your SIII to Android 4.1.1 Jelly Bean in order to use this unlock method.
Warning: This unlock method will NOT work on Jelley Bean 4.1.2. However, if you unlocked your phone using 4.1.1, after upgraded to 4.1.2, the phone will remain unlock. Here are the steps:
- 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
- Put a foreign SIM card into your phone to confirm it’s unlocked.
This method has been confirmed works on the following models:
AT&T Galaxy S3 and Note 2
T-Mobile Galaxy S3 and Note 2
Rogers Note 2
Bell Note 2
Bell Galaxy Rugby LTE
Telus Note 2
Wind Mobile Note 2
T Mobilicity Note 2
Wind Mobile S3
Mobilicity S3 YMMV