Don't pay medical bills unless one has cancer?

I visited the Urologist on advise of my doctor. The statement was R2 710 and Discovery paid R 355.70. I also had to go for cancer blood tests billed R1200 and again Discovery only paid R200. I pay a huge premium every month, but they don't want to pay medical expenses. They said: If the cancer tests were positive (with other word, I have to have cancer) then they would pay, but since the tests are negative, they do not pay for it. How insane?? What is going on at Discovery??? And then they say they don't worry about hellopeter.com posts. Arrogant!