T-Mobile will be the first major US carrier to release a Windows Phone 8.1 smartphone. The company is launching Nokias Lumia 635 this Saturday, July 5th. T-Mobile has apparently thought it best to stagger the phones release; Itll then head to T-Mobile stores beginning July 16th for a promotional price of $99, and MetroPCS will carry the Lumia 635 as of July 18th.