Dischem or Discovery Health at fault for over charging

My 97 year-old Mother uses adult nappies. When I tried to buy them for her through Dischem's dispensary using her Medical Savings (Discovery Health), the price was increased by more than 36%. Price on the shelf is R139/packet and when put through on Dischem's dispensary system the price increased to R175/packet. Why is my Mother not charged the shelf price of R139? Does this disgraceful behaviour belong to Dischem or to Discovery? I think this is shameful and deserves reporting to the Consumer Council for their review. Thank you.