Chronic medication

I am diabetic. Discovery decided that I need to change medication. They have now reduced my one insulin from 500ml to 200. still expecting me to control my sugar. Now when I phone I am told the chemist is at fault. the chemist says they cannot give me more as it is then chargeable. Discovery says it is not end result cannot het medication. Blood sugar from average of 5.8 is currently at 17 and climbing. Oh and the premiums went up above inflation rates again.