Closing a RCS account

I settled my account instore at Foschini in Fourways on the 31 March 2015. I then asked them to please close my account. I was told to email RCS and I've done so. But on 30 April another deb order was taken from my account. When I phoned RCS they told me that I've settled the wrong amount and that the amount that went off my account was intrest on my account. They refuse to listen as to what I have to say and they refuse to close my account even If I've settled my account on the 31st March already.<br> <br> Regards,<br> Kristel