The Samsung Galaxy Note 3, Note 2, Galaxy S3 and Galaxy S4 might be a few years old now but because it came with such powerful specs, the smartphones are still being used right now.
If you are still using one of these older Samsung smartphones and is looking for a way to unlock the device and free it from your carrier. Here is how you can do it. The unlock method uses the leaked code that is said to have been leaked by a Samsung insider.
Put in a new SIM Card and restart the Samsung device. Once the smartphone comes back on, open up the dial pad and key in the code *#197328640#. Now, choose  UMTS >  Debug Screen >  Phone Control >  Network Lock > Options  Perso SHA256 OFF.
Wait for 30 seconds and press back to go back to the main menu. Here, you should see “Network Lock”. Select  NW Lock NV Data INITIALLIZ. Your Samsung device should be unlocked now.