Overcharged while a discount was apl****

I was in the process of making an order and the uber eats app showed an offer saying 50% off when you spend R150 or more. I tapped on the offer to activate it and then continued to place my order. As I went on to checkout it showed that the discount was app**** and that my order would cost R89.90 with the app**** discount. To my surprise when I processed the payment the notification showed that R168.90 had been taken from my account instead of R89.90. I tried to contact support and the number wouldn't go through. When I checked the help FAQ s there was no measure for people who had been overcharged. I will never use Ubereats again as this is the second time this happens hence this time I decided to escalate it to Hello Peter