Sell me a milkshake and tell me it's iced coffee.

I am driving the Johannesburg to Cape Town. It's late, I ordered an ice coffee from engen 1 stop Wimpy Bloemfontein on N1. They give me a chocolate milkshake. I go in to tell them. The entire staff tells me sorry there is nothing we can do. My husband guess on and gives it back to them. What terrible unacceptable service. It makes me not even want to go to engen garages at all.