CLOSING OF ACCOUNT

I have phone RCS call centre asking them for the settlement amount I need to pay to close my account with them. the call centre agent gave me a amount and said this is the only amount outstanding on my account. I did asked them if I pay I know it will take 2 days to show on there side and will the be a problem they said no. I paid my account on the Wednesday when I phoned to close my account on a Saturday they told me they can not assist because there is amount still outstanding how can this be. all the other places I have that I paid on the same time closed my account without any problems why is RCS not doing this. Also I am still waiting for a supervisor to phone me regarding this since the Saturday I phone to close my account I am not happy about this I never missed a payment so why am I treated like this