T-Mobile spoke at Mobile World Congress about the success of their WIFI calling model, which avoid the complexities and fallibilities of handing over VOIP WIFI calls to and from the mobile network by simply only working on WIFI and dropping the call when the user moves out of range.
They announced that around 5 million of its 34 million users were using WIFI calling, many of these on their Android smartphones, and were looking to extend the service to all their Android phones.
Surprisingly Joshua Lonn, Direct of Product Development at T-Mobile said the company was also working to move the service onto the Windows Phone 7 devices at some point in the future.
Naively one would suspect such a service would need a lot of cooperation from Microsoft, but then Microsoft has tried to sell Windows phone 7 as the most carrier-friendly OS at Mobile World Congress.
Read more at T-MoNews here.