Now I am wrongfully black listed

My situation has gone from bad to worse now. An operator phoned me last week Thursday regarding my enquiries over the outstanding amount which Bonitas informed me that they owed me. She said that I was miss- informed (again) and that the Bonitas employee who told me that, had made a mistake. Bonitas apparently does not owe me anything. She proceeded to say that in fact according to the system she could see that my name has been listed on the debt collectors buro - so I have been blacklisted by Bonitas. She said that she can see that it is a mistake as well, as the amount of R236 was owed by me after I left the scheme. She said that she can see that I had made a payment for this amount, but on the system she can not see when the payment was made. It was only recorded in Aug 2014. She said that she will wright me a letter in which Bonitas admits this was a mistake and that she will unlist me. So far I have not received a letter. My credit card applications are being declined. At this point I don't know what to believe anymore. The stories keeps on changing. Please can you fix this. I have spoken to another Bonitas employee and she sounded quite helpful. She's looking into it