BAD COMMUNICATION WITHIN RCS

My loan with RCS was paid up as I took a re-advance. However, since December I have been receiving SMS'S, letters of demand for an amount they say is outstanding. After many phone calls and emails later I got a email with a paid up letter. I thought that was the end of the story. The Sms and letter of demand started all over again. I am at my wits end with RCS, how many more times must I phone/email for them to rectify the error on their side?? How can one department tell me the loan is paid up with a nil balance and another department says I owe money, who is not doing their job properly? I am the one suffering for someone else's error