Cell c is the worst!

My account was in arrears due to unfortunate reasons I then made payment arrangements in October 2021 i was given the wrong reference number by a cell c call agent . I paid my account up to date in February 2022 as per payment arrangements. My account was declared up to date in match 2022. TWO months later cell c informed me that my account is in arrears again for a payment that wasn't made in October. I've sent my proof of payment several times that shows I did pay the account and when I call cell c call center they say they will contact me in order to rectify the mistake they don't. The last time I called the call center agent told me I will just have to pay the amount that's outstanding even though I paid it already. Cell c has the worst customer service in South africa I will never recommend cell c to anyone! Please help.