Cell c is a ****

Cell C is a serious ****, I was incorrectly billed for 5 months and I logged a complaint in June, in September, the manager called and promised to refund me, but till today that has not happened. I have been making follow-ups, but they are just taking me from pillar to post- escalating and giving different reference numbers every time; apparently, they have called me and I didn't pick up and they closed my case. My question is: how do you close my case without paying me??? I have been with this network since 2008, I think it's time I tried others, as I'm no longer valued here.