Debit orders still going off after settlement.

I had a contract with Cell C for more than 3 years and had settled my contract end of december. I had to stand in a long row at Checkers just to pay the settlement amount. After being given proof of settlement and said that my contract is settled, again they took a debit order on end January, I had reversed the debit order on the app and stopped it, but still a new debit order was taken off today. This is utter Bull and quite frankly ********.