Bad Service

Hi, I paid for the settlement of my phone during February 2015 which was updated as PAID UP on my credit record. They later phoned me saying I owe them a balance of R1 016 which I don't understand what is for because they updated my credit information as PAID UP. I'm currently listed as a Defaulter with credit bureau and this has costed me few hundred rand trying to find out why. I had Two contract with them and wanted to upgrade but not anymore. Regards, Victor