Hander over for an up to date account?????

I have been pestered by a company called Near debt management for the last 6 months advising me that I have been handed over by Cell C for 112.94 ref ********** 90 . I contact cell C and they say nope your account is up to date . Try to get someone in their legal department to advise what is happening is even more of a nightmare. I have three contracts with cell c up to date and will cancel them asap. I cannot deal with incompetence like this