Surprise Bill due to no internal communication

On 20/06/17 I visited Dr. Gerber after my assault in order to get a full report on my left eye that suffered trauma. When I made the appointment telephonically, I specifically said that I will need the report for my court case. I completed their patient form specifically telling the reception lady that I will be paying everything in cash directly after my appointment. I asked for the FULL detailed bill and paid the account I received with my debit card (R1 029.80) after I specifically asked if that's the entire bill and the lady said YES, I can just pay next door. To my surprise, on 10 July I received an invoice via email for R620.80 to which I rep**** in shock asking what this is for. For days nobody responded to my mail or returned my calls. Eventually a lady rep**** saying that the account is for the actual report that was sent to me. I refused to pay because nobody informed me that there will be extra costs involved for the actual report (which I had to ask for 3 times) and I specifically asked for the entire bill on the day of my appointment in order to pay directly after my visit. It seems like there was no internal communication and now I am the one who sits with the problem and being threatened to be loaded onto the credit bureau by LEXMED. I will NOT pay this bill due to their internal miscommunication.