Poor poor performance by Commed

I am a Psychologist. About a year ago Commed paid me for services I provided to one of their members. In their statement however they marked it incorrectly as me owing them money. Just to be clear, they did not overpay me, they made a mistake somehow on their statement. Subsequently we have spent many hours trying to solve the matter. Hours and hours on the phone. Sometimes being cut off. Recently we were informed during one of our numerous calls that they had resolved this matter and that it was simply an error on their part which they rectified and would inform the debt collectors. I have now been informed by the debt collectors that I am a defaulter for refusing to pay the R2693.65 that I supposedly owe. I was addmitedly furious and requested a statement so that I could take further action. The debt collectors assured me twice that they would email this to me. SCS (PTY) has to date not emailed me this information. They listen to me and then insist I forward them my proof of payment.