I've used Whatsapp once to actually call one of my friends who lives in Bahrain, and while it works great for messaging her, it didn't work at all for calling. I'm not sure if the internet on one end or the other was too slow or what was going on, but we weren't able to talk at all through it. Usually when we're in Disney, we'll either use Skype or one of my relatives has a magic jack, and that's always worked well for them.