Poor Administration from Cell C

I had contract with Cell C and I paid it up even received a paid up letter on the 28 August 2019 from Maropeng motana. I've been trying to get new cellphone contract but was told that I owe cell C R295 and even checked on my credit report it does reflect that I owe cell c and account still active even though I paid it up and closed it. I went to cell c store to help and was told to call contract department where I was told that I'm no longer on contract my number is prepaid and I'm not owing cell c me R55 according to their records. please assist me in this regard because it is affecting my credit score