Join Date:Joined: Apr 2011
Yes you can, you can change officially via Odin or install custom recovery and flash whatever rom you desire. I got my S4 back last year on o2 then flashed the BTU (unbranded UK version straight away) and now run the Google Edition rom. However I am on the bootloader and can flash whatever I wish without tripping KNOX but only via CWM.
What current firmware are you on?