Unfair credit listing.

I am so not happy with experian. I lodged a complaint regarding the mtn account that I paid off in August last year. They said the want a paid up letter of which I have provided but now they removed the account and placed on adverse listing. Guys please remove this account totally because I paid it off last year. What ever the balance left in that account stated accumulating after I have paid it off because mtn did not close it. That is not my fault I paid all the money that I was owing mtn I even have a paid up letter. Pls remove that account from adverse listing. It is affecting my credit profile because now I can't apply for any credit.