A new method of circumventing the carrier SIM restriction on Samsung Galaxy S III’s and Galaxy Note II’s has been uncovered.
All you have to do is enter a code from your devices’ menu; there’s no need to send information to a website, pay anything or wait for an unlock code.
Note that this method may not work for all Galaxy S III or Note II variants. Also keep in mind that this could void your warranty, so proceed at your own risk. Here are the steps you need to take:
1) Insert the desired SIM card you want to use unlocked into your device, and restart the phone.
2) Enter the code *#197328640# into the keypad and press send.
3) Go to Main Menu ->  UMTS ->  Debug Screen ->  Phone Control ->  Network Lock -> Options  Perso SHA256 OFF (after choosing this option, wait for at least 30 seconds)
4) Go back one step by pressing the Menu button, select back, which should bring you to  Network Lock, then choose  NW Lock NV Data INITIALLIZ.
If you followed the above steps correctly, your device should now work with the new SIM card!
Let us know if the above method worked for you, and on what device.
Source | Via