CellC *****ulantly deducts money from bank account

My retired mother had a contract with CellC and when she was admitted to a frail care centre,phoned them to cancell the contract.Was told she couldn't,whereafter she gave them my banking details.They started deducted money from my account monthly,without my consent.When I questioned this I was told to do a transfer of ownership,buit found out that they should've cancelled the account.I've sent them e-mails to refund all my money,heard nothing from them.I managed to reverse last months payment to them after which they then again attemted to deduct.Once again this month they have deducted.This is ***** and I want my money back!!!