Debiting my account for a contract that does not exist

Good day

I am deeply concerned with Cell C I am currently unemployed, my contract with them ended in 2011, which was cancelled. Over the last 2 months my account has been debited without my consent (9 years later) when I am contacting Cell C no one can explain why. I would like to know who gave yourll the right to debit my account for a contract that does not exist.