Biggest regret was getting a Cell C contract!!!!

I am so tired of Cell C sending MBD to call me on a number that was never even on Cell C. They keep saying I owe them yet last month I was sent a paid up letter because whenever I ask Cell C what do I owe them for they tell me I do not owe them anything. What I do not understand now is why MBD keeps calling on behalf of them. What is even worse the number they keep call was never under Cell C. I am really out of ideas now. The phone calls are now borderline harassment! I am due for an update and I am moving as far away from Cell C as possible. I will take their number with me cos I have had just about enough!!!