T-Mobile will offer unlimited Wi-Fi calling to its subscribers starting on May 11. T-Mobile has been offering this WiFi calling or UMA service for few years and with an extra cost , you will call anywhere in the USA using WiFi without taking your minutes.
Right now you can make calls over a wireless network, which is useful where your data coverage is poor, but on the flipside, it cuts into your in-plan minutes. With this, you can make any calls using wifi for free. Great T-Mobile, keep bringing the good stuff .