Last week we reported about T-Mobile rolling out software update to Nokia Lumia 521 Windows Phone 8 device which enables WiFi calling. T-Mobile Wi-Fi Calling keeps you connected in areas with little or no coverage. For example, now you can make a call from your basement by switching to Wi-Fi Calling. WPCentral posted a video demo to show this functionality which you can watch above. T-Mobile is the only US carrier which has this amazing voice feature.
Read more about the process of getting update at T-Mobile here.