MTN legal department service is pathetic

I took out a sim contract, the benefits I got where not was explained to me by the sales people. I then sent requests for cancelation of contract, in the store I was told to call customer care. I have done that and they failed to cancel for me. I was then handed over to third parties for collections. I paid that amount in June 2021 the account had already been listed as a default. I have then been paying the account then I realized that I am still listed under defaultees when I wanted to apply for credit in other places which I could not be granted. I have been calling their customer care, I was given an email address for their legal team. I sent numerous emails with no response at all. I'd like it MTN to please clear the default under my name. It's been more than six months now that account has been paid