I've been using this UMA wifi calling feature for 2 years on my Blackberry bold 9700. It works all over the world, texting works too! When I leave the country I turn the mobile radio off and only hop on free and hotel wifi spots. making and receiving calls for free.. Europe, Japan, Cambodia, Thailand, Vietnam, Australia, New Zealand, Canada, Russia all work great! Mind you, I can only call the USA, as it's just like I was in the US. No mins deducted from my plan and I can keep in touch with SMS and MMS!!!! Love it! Tmobile rocks. And I always have a signal where there's a wifi! Calls are clearer than cell calls too. Rocks.