Refusing to acknowledge wrong order

I made an online order (Uber eats) from McDonald's Cape Road Drive Thru. 2 Big Mac's and a Caramel Chai Shake for R300.90 . What I received was a small spicy burger with chips and coke when i refused to take it they said they wont refund me because i refused the order. So I don't know how must i accept an order thats not mine and everything i complain on the app nothing happens they are not even answering the phone