How do I update s6 edge

Need to know how to update my phone it's a rooted galaxy s6 edge cellcom and it doesnt show up any downloads on Samsung page and neither does my carrier, or my exact model number but I have seen ones with the same shorter model number which is sm-g925r6 is there a custom rom that's safe to flash or even a way to update it not being able to find my carrier, by the way cellcom is a smaller carrier which is CDMA and runs on their own towers, but all across the united states. It's currently running 5.0.2 and I've updated it ota once but it still has the same android version. Any help is appreciated, thanks.