Unauthorized deductions from my bank account

I have cancelled my contract and paid the cancellation fees as quoted by Cell C but a ridiculous amount of money has been deducted from my bank account the end of the following month. I was charged again for the cancellation of my contract although I paid the amount cash already. Numerous mails was send (have about 10 reference numbers) to settle the account but only after I receive answers on my questions. Once again last night there was the same amount being deducted from my bank account. I need some serious assistance please. Everybody is trying to phone me to assist but they make promises and never get back to me.