bad service, i want my account closed

i have received a terrible service from either RCS or Coricraft accounts department. I called on the 17 October to close my account and asked for a settlement amount. Same day i paid the settlement. Coricraft is still billing me for their service and interest which i do not know from where. when i call the call center i keep being transferred to wrong department for loan applications. i wanted my account closed and i do not want to do anything with coricraft. Why charge interest on an account that has been settled?