Contracts Cancellation

This is the second time i cancelled a contract with cell C and having endless problems. I cancelled my contract in June which they double charged me for the cancellations fee and they apparently fixed the issue. I got a call from head office and the guy there told me he fixed the issue and i don't owe cell C anything. This morning they debit my account for R4600 when i don't owe them a cent. This is unacceptable!!! the last 6 month with cell C has been hell for me. I need this reversed immediately!