Newfound support in iOS 8 for Wi-Fi calling means that T-Mobile will finally be able to offer the service to its iPhone-toting customers, which Android and Windows Phone owners have had for years.
In the carrier context, Wi-Fi calling connects calls using your Wi-Fi network in times of weak signal on T-Mobile's own voice network. As long as it's turned on in the settings, the switchover is automatic and free, and calls over Wi-Fi naturally count as talk time, not as data usage.
T-Mobile says that once iOS 8 makes its way onto iPhones, Wi-Fi calling will blanket 90 percent of the phones on the company's network. The carrier hasn't said how many phones are compatible with the service now.
For existing customers, Wi-Fi calling is essential in making calls in areas short on signal strength, like rural locations. Sprint, too, switched on Wi-Fi calling in February of this year, extending it to five handsets, including theand the .