While both the Samsung Galaxy S4 and the S3 are devices that have been on the market for a while now there are still many people who own them. If you are the owner of one of the devices that is locked you will be pleased to hear that you can now unlock it and take the handset to a different carrier.
The first step to unlocking your Samsung Galaxy S4 or S3 is to take a new SIM card and put it into the handset. You should then switch the device on and then go into the dial pad. Type in in *#197328640# and then follow the steps which are outlined below.
Next go to  UMTS >  Debug Screen >  Phone Control >  Network Lock > Options  Perso SHA256 OFF.
You then have to wait for around 30 seconds and you can then head into the main menu and choose Network Lock and choose  NW Lock NV Data INITIALLIZ.
If things have gone to plan you should now have the Samsung Galaxy S4 or S3 unlocked and this means that you can take the handset to the carrier of your choice. The code also works with a number of other Samsung devices so try it on yours.