Cell C and Nimble Group

I'm currently trying to get my name cleared by Cell C, they had sold the account to Nimble Group which was opened **********ly under my name. I received a confirmation letter from Cell C and I was promised that my name was to be cleared, this was last year already. I contacted nimble Group and they said they have escalated the matter, this was August last year, the account I'm talking about is showing arrears of R3410 on my name which is affecting my name. I want to buy a house but with this arrears in my name I can't get decent credit. My credit score has been very poor because of this. This year I have contacted Nimble Group who refused to clear my name as they say they are still waiting for feedback from Cell C who gave me the letter. South african ***** prevention also confirmed that my ID was used **********.

I would like your assistance as I don't know what to do next.