Shocking Cell C

Good day, I took out a contract with Cell C In Feb 2022, later that year I changed banking details. After numerous attempts and calls they never updated my details, resulting in Debiting the wrong account up to 5 times a month at a charge of R145 per time, resulting in bank fees over R5000. Then someone called me again and I said i deposited money to that account they can debit at month end. The next I get an invoice for contract cancelled and a debt collector wanting R16000.

Please sort this out! I can not afford a R16000 bil.