Unauthorised Payment by ********* called uber eats

Yesterday afternoon around 15:00 i placed an order through uber eats and the total amount of my order was R118.80. I clicked on my 80% promo code and showed that it has discounted the order to R31.80 and that did not apply after clicking on placing order. I ran down to KFC to get them to cancel the order and I was told that only uber eats can deal with it. I left my food and paid for a fresh order with cash thinking uber eats will come back to me. The store manager however called uber eats for me due to long queue, I ended up leaving and rushed to work to be contacted by uber eats via email telling me that the receipt shows that the discount was used and they are closing he complaint. How is it possible that they **** me, took my money off my card however still sends receipt the next day that confirms the wrong amount they charged. I want money from these **********.