Not cancelling the contract

I have tried to cancel my contract(a contract that is no longer valid) for the last 4 months. But still every month R400-R500 is debited out of my account due to the negligence of Vodacom as a company. Please can someone from the accounts department phone me to cancel this. I would like a refund for the debit orders that have been taken off as I requested this 4 month's ago. All the phone calls were done from the same number and should be easily tracked on recordings.