CONTRACT PAID UP BUT STILL SHOWS IN ARREARS

am so disappointed in mtn services, i have a contract with them that was taken to legal in 2019 and i then finished paying it off in 2020 but to my surprise the account still says am in arrears with R991 and it has been messing up my credit history, i can't even make applications for other products without it popping up with its ugly arrears, I've called and sent emails with no proper information, i wanna take them to the ombudsman office am tired, i don't want anything to do with them anymore. they are ***********, so unprofessional.