How do you refund R20 for an item that cost R68.80???

I placed an order today literally less than an hour ago and received 2/3 items I ordered. Pizza Hut has been ****py considering previously they delivered incorrect items and today I have my pizza and chips worth R68.80 and you credit me R20 bucks for the item I paid for that was not delivered. My chat is closed with no satisfactory resolution and no more options to have this resolved. I definitely want my money back, ask the driver who delivered my order if I didn’t query the missing item and he told me he didn’t get it. Nonsense Ubereats, improve your investigation process cause the hell is this.