Inflexible Cronic Medication Procedures

I have been registered on Discovery to receive my chronic medication for hypertension. My dr recently changed to dosage of my medicine to test if my body responds better to the medicine. I went to the chemist to get the revised dosage hypertension medicine and had to pay cash for this as I was told that Discovery no longer cover the medicine from my chronic benefit. I phone discovery and they finally got back to me telling me that I have to submit a new prescription for the revised dosage medicine to be registered as chronic. This is ridiculous. I have handed the new script to the chemist. I do not have a copy of it. Surely the chemist dispensing the medicine to me and claiming from Discovery should be sufficient for Discovery to amend my chronic benefit accordingly?