First world problems I know. 
I find that most of the time, despite listing "Coca-Cola", takeaways etc almost always send Pepsi instead.
It's not as bad as sending the diet version (ugh) so I wouldn't complain, but it's still not as nice and isn't the same drink. I suppose they do it because it's cheaper.
Was in a restaurant once and the guy tried to convince us that coke and Pepsi are the same drink and are made with the exact same ingredients...!
Explain the different taste then. 