Unprofessional conduct.

I booked for an appointment with Dr Leanne. What was an existing day turned out to be very disheartening. I was informed that I had a 3 year outstanding amount due. My bank App and their account shows I paid. They have no explanation and can not give me an invoice. I now over paid. There is no payback no explanation and no, we apologies. Just silence from their side. They didn't want to help until I paid outstanding amount. I did this and then went into my account and saw that I indeed pay them in full. I am disappointed for the way I was treated. I have never had such an embarrassing experience anywhere before. My review on them would be. Check for and demand an invoice or receipt.