Telkom Phone contract

I had a phone contract with them which I paid until the end.comes from nowhere I received an sms from nudebt that I have been handed over by telkom that I have missed payments and 1 of telkom consultant told me my account is paid up and they handed me over without even talking to me that I owe them they have just do it and I don't owe them as they advice that am done with a contract.okay then I called them Why did they hand me over they said am owing 322 for closing the account which they didn't even bother to communicate with me then I paid that amount by December but still its says I still owe them and my credit score is drowning because of them even nudebt they giving me run around asking to send proof of payment which I did 5 times every time I call they giving me stories am tired need help cause my score is drowning