Cell C

I've ended my contract with cell c in 2019 and they still deducting from my account. Last month it was R1,100 this month R1,400 besides the previous debits. Had to go to my bank to reverse ,and that gives me a bad credit record. I've contact cell c and they told me that they don't have any record of debits that's going off my account and my that number is on pre paid.I went to cell c store to quiery about my problem,and they said it's because they give me data every month but I don't have that cell c sim card for over a year. I really don't understand why this is happening. I need help please... Kind regards Amanda Hammer