If I'm in Japan, I'll rent a phone from Softbank. In India and Krakow (most recent trip to Europe) Skype was the bomb. Otherwise, I put the phone in airplane mode, turn off all cellular data (overkill I know, but it's useful when you want to use the phone's gps and need to toggle airplane mode off momentarily) and turn wifi on. I wouldn't rule out renting a MiFi at some point in the future and relying on a combination of it and Skype.