In case you happen to own one of Samsung’s 2012 flagship smartphone, either the Galaxy S3 or the Galaxy Note 2, you’ll be happy to hear that you can unlock them from the shackles of your carrier free of charge. And you can do all that by yourself, as long as your handset runs a Jelly Bean version.
Naturally, we don’t encourage you to go for such procedures in the first place, and unlocking a handset that was purchased with a new contract agreement will surely be frown upon by your carrier.
But in case you want to use the Galaxy S3 and/or the Galaxy Note 2 with another GSM mobile operator, or sell the phone to upgrade to a different device, you should definitely check out this method.
xda-developer owl74 found a hidden menu in Samsung’s software that lets you perform the unlock from your own home. The method works on the GT-N7105 but other Note 2 models as well as some Galaxy S3 versions will let you do the same exact thing.
Redmond Pie describes in detail the steps you need to take to unlock either handset:
Step 1: On your Galaxy Note II, launch the phone app and press these keys:
Step 2: From the Main Menu, navigate to  UMTS > Debug Screen >  Phone Control >  Network Lock > Options.
Step 3: In the Options screen, choose  Perso SHA256 OFF. Wait for 30 seconds after making this selection.
Step 4: Go back one step by pressing the menu key, and then back once. You should now again be in  Network Lock
Step 5: Here, now choose NW Lock NV Data INITIALLIZ. Wait for one minute after making the choice.
Step 6: After a minute has passed, reboot your Galaxy Note II.