discovery deny us services

i have discovery s my medical aid but sometimes things turn to be worse for my finances cause they dont pay all my medication ,always i visit a doctor they use my medical saviings and its got exhausted ,and now i had a shoulder operation refered by chronic doctor whom they pay from scheme but i didnt get pain medication from pharmacy after my operation i was suffering pains ,now i need to collect my script ,they say to me they wont pay for syilpane why,i no longer want to use prednsone it damages my bones but they argue that they wont pay for it and the doctor even prescribed it for me is this fair or what