Suprise R3550 co-payment

I was admitted to hospital early this year, pre-authorized with Discovery medical aid and everything seems fine.<br> I was told that all the procedures done will be billed to my hospital benefit during my stay. After some tests, they decided to perform a gastoscope to ensure the condition wasn't reflux related. All went well an til months later I received a call from the hospital saying I have a co payment of R3550... apparently for using the facility, (hospital, that I was already using) while doing a gastroscopy. I called the help desk, and they say \gastroscopy done in hospital has a co-payment\", fair enough, but I was not admitted for a gastroscopy, it is not the same thing as having a co-payment because you need to be admitted. I was already admitted and pre-authiorised and I was currently undergoing treatment for the planned admission, it was during this time that the gastroscopy was done (6minute long procedure). the hospital is not double billing the original admission aswell as an admission for the gastroscopy. besides, the total gastroscopy costs are under R1000, I have a co payment of R3550. After speaking to a CRM, Rentia Patterson could not understand the situation.. "