MTN Unfair credit bureau listing

I had a contract with MTN, which I settled in August 2024 and received a settlement letter. Due to the change of laptops, I can no longer access the letter. After realising that I have been unfairly listed for the amount of R144, which was invoiced after the account was closed, I cannot receive assistance from VCCB because the MTN email with the reference number alone is not enough evidence for them to clear my name. MTN, on the other is unable to assist me; All I see is email communication to and from their legal, customer service and complaints division. This is one of the worst experiences I have ever had with a network service provider. It's a huge setback. My name and credit score are negatively affected. I regret ever having dealt with MTN.