8ta's 2+1 GB deal is about the best around, AFAIK, for R149. It's not automatically loaded monthly, but you are in control of this yourself, and it will in fact stretch into the next calendar month if you still have some balance left over at the end of the month. Works for me!
Cell C indeed launched its highly-trumpeted campaign to blanket the country with its own towers, but then somehow ran out of steam around the time the last CEO left. The very large city of Rustenburg and its environs, for example, has been promised dedicated Cell C coverage for well over a year, and many of us have now simply drifted away to other providers in despair.