Co payment despite been on non network

I needed retina surgery at Garden City Clinic. It was urgent because i am blind in my right eye. I am on MedSaver non network which means i can go to any private hospital. Medihelp issued me with an authorisation number with a co payment of 35% . I spoke to a consultant at Medihelp who informed me that Netcare Garden City is not on their list for Retina surgery. This implies even if you on non network cover , certain operations can only be performed at certain clinics despite you paying for non network cover. I am a pensioner , now i have to pay an upfront fee to the clinic.