Flat Carbonated drinks

Upon receiving our Coke Zero at the kiosk, it was obviously completely without carbon gas and tasted flat. Although we brought this to management's attention, they said that there is nothing they can do about it. We were offered An alternative drink, but this was a sugary drink and it seemed to us that it runs off the same system and will have the same results. Why is there not a proper alternative to the soda fountain options? I.e can or bottle? How can we be charged R60 for old popcorn, small chocolate and a flat drink? This is ridiculous..