i-Mobb, the Free Roaming App (Android, iPhone). Make and receive calls on your device with no roaming charges for the duration of your trip.
i-Mobb is an App currently used on iPhone and Android devices. With this App, residents of 38 major countries, traveling anywhere in the world, can take their smartphones (or tablets) to make and receive unlimited calls without any roaming charges. The service cost a minor fixed fee based on the duration of the trip. Unlimited calls can be made to 60 countries.