RCS billing *****elent as account was paid in full

I called in the call center and obtained a full settlement amount which was R13998 , this was done and paid on the 6th October 2015. After completing the payment I called into the call Centre to close my account with RCS as they always seemed by be adding interests charges in between transactions of payments sometimes almost 2 times a month. I eventually death with several agents who told me they couldn't help me as they don't know which department does this. 10 days late on the 16th of October 2015. I am billed with a statement showing I owe R179 for interest from the 6th to the 16th October on a balance of R0.00 outstanding. I am seriously dumbfounded by the length that this company will go to keep people in their books.<br> <br> Can I sue them for messing with people and hiring dumb managers and call center agents who keep saying they cant help you, thereafter cutting the call on you. I wish I never did business with them, my experience is totally frustrating as no one can assist you to close your account with them. I just hope my letter keeps prospecting customers away from them. I will be airing my experience in as many social media websites on my experience with RCS.