Css Credit Solution is *********** and exploits people

I had an account with foschini that was handed over to css credit solution. I called in to request a settlement amount since I wanted to settle my debt. I paid and requested a paid up letter which was emailed to me. I was then shocked when month end I received a call to pay foschini an outstanding amount. I told them as far I know the debt is paid off I received calls on a daily basis, I have spoken to managers and supervisor, I even went as far as going to the branch personally They all say they will get back to me but they don't call or resolve this. I keep on getting emails to make an arrangement they have even blocked my number I can not even call them back. I recently checked my credit status and the amount keeps increasing this is exploitation and unfair because I have. a paid up letter and settled my debt they need to rectify this.