MTN contract

Good day

I have an active contract with MTN, last year they missed few installments due to wrong information captured in their system which I then later settled the outstanding amount in October 2020. Now I’m in the final stage of buying a house and to my horror I discovered that my name is listed with the transunion credit bureau. Iv been calling MTN but no one is will to help me, at some point a lady I was speaking to hanged up on me.iv been sent from pillar to post trying to resolve this. The bank is requesting me to provide a clearance certificate from MTN to show that I do not owe them but MTN is failing to give me that. What is even more pathetic is the unwillingness from MTN to help in this regard. I have logged a call with MTN but no communication has ever been made and I’m just told that the file is still open even after 72 hours that I was told it will take to resolve this. The sellers are now threatening to pull out of the deal and I stand to loose a lot of money as I have already paid for lawyers.