Cell C mobile data horror

Roaming continuously comes on as cell C is never consistent with their signal. I've had 5 SIM swops in a few months. How can I not have Cell C 4G as an option for my registered network if selected manually? Mobile data won't work , and if you don't have WiFi, no apps are usable. It is ridiculous. I'm faithful, and really don't want to change, but this means anytime I leave the house , I am not reachable other than by an actual call. Not fair at all