Discovery health do not care about health of it's members

I am a member of discovery, was diagnosed with a condition that they approved chronic treatment.When I present a Dr's script at the pharmacy, was advised that the medication is not on the list. I'm paying premiums every month, have been on their medical aid for more than 15 years yet this is the kind of service I get when in need of treatment. This is unfair given the length of membership and the medication is not even expensive. If it is not on the list, they must add it on the list because I need it.