Poor service

I just bought a 9 piece bucket and a Chocolate Milkshake at KFC Tzaneen mall Danie Joubert. My Milkshake was given to another customer instead and the customer left the store with it, when I asked for my Milkshake they went outside the store and looked for the other customer and came back with the Milkshake. They expected me to take the Milkshake that was out of the store with another customer, when I complained I was told that the other customer had not drinked my Milkshake. I found myself leaving the store without a Milkshake that i paid for and without an apology. I am very disappointed in the service that I got.