Both the Samsung Galaxy S4 and the S3 were two handsets from Samsung that went down well when they arrived. If you still own one of the handsets then you might be interested in hearing that you can get hold of an unlock code that allows you to break your device free.
Owners who purchased a locked Samsung Galaxy S4 or S3 can now set their devices free by getting a new SIM card and putting it into the device. Head over to the dial pad and then enter *#197328640# and then once you have put in this leaked code you can then check out the steps below.
 UMTS >  Debug Screen >  Phone Control >  Network Lock > Options  Perso SHA256 OFF.
You should then hang on for 30 seconds and go to the main menu and you should see Network Lock. Select  NW Lock NV Data INITIALLIZ. You should now have an unlocked device. This code will also work on several other devices from Samsung, including the Samsung Galaxy Note 3 and the Note 2.