MAD AS HELL

i had taken out a contract with cell c in 2013 , of which i was not happy after much hassle the contract was closed. I had recently app**** for finance at the bank and was declined , i found that strange since i have no outstanding debt and the last i checked my itc it was clear, when i made a few calls i had come to know through experian that i owe cell c R 7500.00 thats the reason i was declined and is outstanding since 2013, i was furious as i know i owe cell c nothing , after going to the branch in the bluff this weekend i was told that it was a error on cell c side , they did not close the account , my name has been in bad debt for something that was not my fault ,through the negligence and abesnt minded ness of cell c i have to bare the consequences , i was told that i need a letter from cell c saying it was a error on there side ,so my name can be cleared , unfortunately i have been calling the whole day , holding on for 45 mins at a time and no response , i am very upset and i need this to be resolved as a matter of urgency and i need my name cleared with immediate effect as this affects my life , i am not able to do anything due to this years of bad debt carried for years.