Unfairly defaulted my name and listed my name..

I settled my MTN contract account since January 2023, they said i must wait for 21 days before they can update my account from Credit Bereau. It's been 4 months now, the defaulted me. I've been calling them everyday to fix my account, I'm unable to Open any account at anywhere, my credit score is busy going down every day.... Mtn is Doing Nonsense... I'm so fed up. I'm so gatfol