U.S. wireless carriers like AT&T, Verizon, Sprint and T-Mobile have supported Wi-Fi Calling for some time now, with AT&T, Sprint and T-Mobile also supporting Wi-Fi Calling on other iCloud-connected devices like iPad, iPod touch, Apple Watch and Mac. According to user reports on MacRumors' forums, iOS 10.3 beta 1 supports Integrated Calling on Verizon.
With this handy feature, compatible iCloud-signed devices can make and receive calls using your carrier's account even when your iPhone isn't nearby.