Bad service

I had a Cell C contract, when my contract term ended they continued to debit my account saying I did not cancel the contract. We had a back and forth as I understood the term was finished meaning I am done paying. I didn’t pay the amount for some time and this year I kept paying it R200 and today I called the customer care wanting to make settlement. I was taken from pillar to post. I visited Cell C Brits mall and the consultant indicated to me that in her system the amount reflected a minas meaning is an amount due to me. We then proceeded to contact the customer care to request a paid up letter. Which I will receive within two days. The consultant from the customer care also kept telling me there is no settlement amount that I owe Cell C. The same account is affecting my credit score. Cell C must refund me as I know I had finished my contract with them.