Cell C - FINAL LETTER OF DEMAND - For a Account that is closed

Good day, I logged a dispute with Cell C for a Fibre contact that was closed and settled in September. I received a letter of demand on the 31st of December 2021 stating I owe an amount of R1249,16. I paid these funds to Cell C to clear my name. I then contacted Cell C regarding this and there was simply no explanation as my account had been closed since September. My latest credit check shows that I have defaulted 3 months in a row for October, November and December for a contract that has already been settled. I need to be refunded and my name needs to be cleared for the past 3 months. I am unable to apply for credit because of this infringement.

This needs to be escalated to the credit regulator,