Incorrect credit bureau listing

Early last year, cell c called me and offered me a contract phone, but when it was delivered it was not working up to standard so I returned it without using it. However they billed me for R100 and listed me on credit bureaus despite having gone through the cancellation process. I even had to write a review about my experience on this platform and they started helping me, or so I thought. However, after a year since the cancellation process my credit report still shows an active cell c contract with a balance of R100, and I don't understand why. Could someone from cell c please explain what's going on?