Owners of the Samsung Galaxy Note 2 and Samsung Galaxy S3 who have a device that is locked to a carrier may be happy to know that they can unlock the handset for free. When the device is unlocked it can then be used anywhere in the world, providing of course you are not tied down to a contract.
For instance if you purchased the AT&T version of the handset in the US, you are only able to use the handset with that carrier. If you unlock the device you would be free to move to another carrier. You could even send the device to a friend or relative overseas and they would be able use it with whatever carrier they wanted. So here is how you unlock your handset.
This applies to the Samsung Galaxy S3 along with the Samsung Galaxy Note 2.
Put a SIM card into the handset that is not from your carrier. Turn the device off and on while the SIM is still in place.
Open up the dialpad and key in *#197328640#. Go to Main Menu >  UMTS >  Debug Screen >  Phone Control >  Network Lock > Options Perso SHA256 OFF > then wait for 30 seconds or so. Then hit Menus and choose Back. You should now see Network Lock. Then choose  NW Lock NV Data INITIALLIZ.
To make sure you didn’t make a mistake, the sequence you should have typed in is: Asterisk Pound One Nine Seven Three Two Eight Six Four Zero Pound. However some people call the asterisk the star button and the pound button is sometimes called hash.
You should now be the owner of any unlocked version of the Samsung Galaxy S3 or Samsung Galaxy Note 2 and you will be able to use any SIM card in the handset. Samsung has been using this code for some time so it may work on other types of devices too.