Regardless of operating system, those devices include RIM, Android, Windows and its soon-to-debut Symbian-running device. Wifi is standard throughout the World and this will be a breakthrough for many travelers who are constantly purchasing multiple phones and SIM cards to make phone calls while overseas..
T-Mobile has been a popular way to make free phone calls for many World travelers with UMA Blackberry phones. In addition to cost savings, WiFi calling enables T-Mobile to extend service to difficult-to-access areas, such as malls, hospitals, stadiums, parks, schools offices and its millions of dead zones around the world.
T-Mobile has 152 million mobile customers served by the mobile communication segments of the 119 million Deutsche Telekom group & 33.8 million by T-Mobile USA -- all via a common technology platform based on GSM and UMTS, the world's most widely used digital wireless standards.