Cell C unauthorised debits

I paid off and closed my contract a couple of months ago and yet Cell C keeps debiting my account. When I call they say they won't any more. I have put a stop to their debits but they just keep doing it. I went to ABSA to check how it is happening they told me that Cell C just changes the debit reference number and slightly alter the amount so that they can keep debiting without my authorisation.

Stay away from Cell C contracts people!!!! If you have closed your contract with them check with the bank if Cell C hasn't change their debit reference just to keep debiting you.