Incompetency of cell c

On the 26th of July 2022 I learnt that Cell C have listed my name at ITC as a bad debtor for a contract which was settled on the 31st of October 2021, to my surprise when I made an enquiry on the said date they informed me that it shows in their system that they are the ones who owes me. When I request for my name to be removed from ITC they keep telling me that their back office will get back to me in seven working days and it has been a lot of seven days as well as too many apologies but my name is not cleared