Cell c and my paid up letter

I had a cell phone contract with cell c 4 years ago and paid up the contract however a few months ago I checked my credit profile and discovered that it reflects a balance that I owe them I immediately called to find out weither it is true just to find that its not true I was so upset as im always being denied credit everywhere because they are prohibiting me from accessing any credit at the moment I sent emails and call them repeatedly to have this sorted and requesting a paid up letter everytime the agents assisting me promise il receive it within 48 hours its been two weeks now going into the third week I have still not received any feedback from their managers who I escalated the issue to or any paid up letter not sure what to do please assist I would like my name to be cleared. I received two reference numbers and evertime I call I get told that your query is still pending and haven't been look at but promise a paid up letted within 48 hours how if no one has checked my query. Please assist as by law it is not right to store inaccurate information on a customers profile and prohibiting one from getting credit elsewhere.*** and *** this is my reference numbers please assist.