Poor service, Missing items, CheckersSixty is a ****

Order # :***7

I placed on order with CheckersSixty60 on the app on Saturday morning. Not only was I disappointed to learn that the "delivery in 60minutes" is just a **** and marketing gimmick. They delivered my order with 14 items missing. I was travelling and had no means of being to purchase those things again as they withhold the refund in the app and not directly into my bank account. I contacted their call center, and the asked to speak to the manager and they both did little to nothing to change the situation and help. On top of this mess, my total order amounted to R1059.72... the items they delivered add up to R438,86... however the credit reflecting on the app is R514.88???? According to my calculations, it should be R620.86... Does anyone know how I can go about claiming all due to me and not being ****med like this? After their poor service?