Cell C (ripping us off)

I have been have a month to month contract with cell c for a monthly fee of R20.00. I then decided to cancel the contract but to my surprise, my account was debited. I then reversed two transactions(R20.00 each), after some days my account was debited with R173.80 which I reversed. I lodged a query online and was told I was upgraded which I never did and the person who was on the did not even tell me when I upgraded. I received messages from their debt collectors but they failed to send me statements. I received a call again two or three weeks ago and the lady told me they cancelled the contract cause I did not pay but could not even tell be when was the last payment made.