Contract phones

Good day I bought 2 phones that I bought from Vodacom Queenswood I was supposed to pay it until July 2025 however on the 17th September I called Vodacom agents to request an early cancellation they gave me a cancellation they gave 13 days to pay if not there could be charges so I ensured that I paid everything on the 20th now I am getting calls from Vodacom saying that I have a balance of R400 or more each time I tell them the story they promise to call me with a clear information they never do and I get calls everyday with no solution to this problem only promises to investigate and call to clarify, this is frustrating when you are trying to close debts but paid people claim not to be fully paid I even went back to Vodacom Queenswood they assisted and told me that on their side the account has been paid up but the agents keep calling.