Roaming data is like $10 for a week these days, is it really worth messing with WiFi calling just to save a few bucks? Sounds like the barista was just messing with you, not like the call was actually broken bad enough to ruin your day. I've had Skype go fuzzy in a cafe before and nobody handed me a passive aggressive note about it. Maybe the problem was the coffee shop's router being overloaded with tourists, not the technology itself being a disaster.