Discovery medical aid

When I was working at Wits RHI, I had medical aid which was part of the package, when I got retrenched they were still paying for that medical aid. I had to be admitted and when through operation. To my surprise I then received a bill that medical aid didn't pay and I have to pay. I have been paying the money as much as I can afford. May you assist with this account as i do not understand how i am paying the bill if i had medical aid.even if the medical aid was then cut, does not medical aid come with insurance that i do not accumulate a bill? I have been paying but the bill is still so much. My name is Ndangano Mashashane (nee Makongoza), ***