Exessive billing

What the hell is going on??? My data contract (R99pm) ended four months ago. I went in to a store to find out what the problem was and had to cancel my contract after an amount of R279.00 was deducted for two months after. According to the consultant, the contract was then cancelled with my last payment end of August. Another deduction of R279 went off this morning, 1st of October!!!!! Can you not manage your agreements with customers??? Why must a contract be left for the customer to be cancelled although a 24 months agreement was signed initially??? I wonder how many other customers are victims of this type of mismanagement!!! Cell C wants to buy out other contracts, but cannot even manage the ones they have!