Why will you not pay Discovery?

I need someone in senior management to explain to me why Discovery will not pay for meds that i need. I had to remove my husband from my medical aid so that i can go on a higher plan to get meds covered and still i have issues with meds not being paid. My salary is not great, but around every corner i have to give out of my pocket for whatever discovery will not pay. I just need to understand! Why Discovery. Why?!!!