Can't define APN: "Unfortunatelly, Settings has stopped" - SG 4
I had the same problem. All you need to do is back up all your data using Samsung Kies 3. Download it from their website (Samsung.com). Then do a Factory reset. Once reset is complete on your S4 you will now be able to Edit the APN. If you have a contract with a provider ask them to send you the settings and your Internet data will work. Mine is now working all okay. Hope this helps.