Cancelled but still debiting

So my mother's one contract came to an end and she contacted client care to confirm. They said last month was the last debit but her account was debited again for R390,00??!!. Her existing contract is R106,00 per month but they debited more than that, how the hell is that possible as it is not an open contract. I demand that you pay back the R390,00 and rectify the R106,00 or you will have a another Cell C Suck banner on your hands. My number is *** as she is fed up calling your client care.