A Verizon spokeswoman confirmed to FierceWirelessTech that some iPhone users can make Wi-Fi calls, but there are some conditions. Users need to have advanced calling enabled on their iPhone, they need to download the latest Verizon Messages app from the Apple App Store, and they need to enable calling within that app. If a call is being made from the native dialer, it's still going to go through the cellular network.

The Verizon app works with Apple's (NASDAQ: AAPL) iPhone 6, 6 Plus, 6s or 6s Plus. It's not yet available for Android users, according to Verizon spokeswoman Kelly Crummey. She did not say when that might be available.

Last year, Apple added support for Wi-Fi calling in the iPhone 6 and 6 Plus, but operators need to make tweaks on their end in order to enable it. AT&T (NYSE: T), Sprint and T-Mobile already support the feature. Some Verizon customers have said they want to use Wi-Fi calling because they live or work in a dead zone, and network extenders don't always solve the problem.

Last fall, Verizon Communications CFO Fran Shammo said Verizon needed to do some technological work to make Wi-Fi calling available, but he said that it would probably be available around the middle of this year. That window came and went, but with this release, it's now available to at least some of Verizon's customer base.

Last week, AT&T launched Wi-Fi calling on the iPhone 6, 6 Plus, 6s and 6s Plus via Apple's iOS 9. Once the service is set up, which customers can do via their settings on their iPhones under phone settings and Wi-Fi calling options, AT&T said customers' phones will use Wi-Fi calling automatically in places where they have limited or no cell signal alongside a Wi-Fi connection. AT&T said Wi-Fi calling works in the background, allowing users to make and receive calls like they would on the carrier's cellular network.

T-Mobile US (NYSE:TMUS) has offered Wi-Fi calling since 2007 and about 12 million Wi-Fi calls are made daily through its network. It also says it is the only U.S. provider to offer seamless handoffs between VoLTE and Wi-Fi; however, AT&T also supports seamless handoff between VoLTE and Wi-Fi, according to an AT&T spokeswoman.

Sprint has made Wi-Fi calling available to its customers (Source:bidnessetc.com)

Sprint (NYSE: S), which considers Wi-Fi a complementary "fourth layer" of its network, also has made Wi-Fi calling available to its customers for quite some time.

Wi-Fi operators and supporters have long said that Apple's move to support Wi-Fi calling last year provided a big boost for their cause. Strategy Analytics expects the market for native Wi-Fi calling, which lets users make and receive calls and texts on their smartphones just as if they were on the cellular network, will grow rapidly in the fourth quarter of this year.

fiercewireless.com