Accounts

I went to the emergency unit in May 2016. I got attended to by the doctors and a few weeks later they sent me the bill and informed me that my medical aid had not paid them because my savings had been depleted. However i made a payment plan and settled the amount. Today 04/04/2018 i received a call from Blake Associates. The agent told me i owe the Groenkloof hospital R915. I told him this should be incorrect as I settled my account. He gave me a number that i should call from Groenkloof hospital. I called them and I am being told i owe R915 even though i was never admitted to the hospital and i never received any invoice from them. The guy said i should escalate the matter with his manager. The people from Blake Associates called me again and said if i need an invoice i should give them my email address. I refused, you are saying you got my details from the hospital but you do not even have my email address how does this work? So i should just pay without seeing any invoice and description of what i am paying for? He then said i should expect a call from other departments more like threatening me that the matter will be pushed further. For an invoice i never received and payment i was never informed about? So why are they only telling me now about this 2 years later?