Shortage of an order

My brother ordered full chicken and chicken breast from Uber eat we only received chicken breast and quarter chicken. When we went to pedros dobsonville to complain, they told us it's not their fault it's Uber eats fault, and never said anything about refunding him or giving him half of the chicken they blaming Uber eats, So why they keep on using Uber eats. While he paid full price. We have a proof of payment kindly solve this issues cos it not happening for the first time, we would like a refund for this one we've been quite for some time now