MTN Ruining my Credit report

So I had a contract with MTN 2 years ago, it so happened that I defaulted the payment. I was later referred to the lawyers by MTN and I settled my account, yet the default payment is showing on my credit records. I send my complain via email and on facebook a month ago, and I'm still not assisted. You cant talk to an agent since their contact number is so complicated, MTN must just close shop!