Not reponding to my cancellation of contract

I had a contract with cell c. I cancelled it the end of May 2015. I paid the cancel fee they asked for. They deducted end of July, end of Sept twice because there was no money in Aug. I phoned them since July 2015, all they say is we are looking into the matter and I must always speak to a new person and explain myself over, I also asked to speak to a manager but nothing happens with that. They don't phone back or let me know how far they are. I want my money back from them (all of it). They tell me every time a different amount that I would get back from them.