More Australians stuck in mobile blackspots will be able to make voice calls over WiFi as Apple's iPhone joins Samsung's Galaxy smartphones in supporting VoWiFi on Telstra.

Third-party apps like Skype have supported WiFi voice calls for years, but telcos are naturally slow to adopt any kind of technology which would seem to eat into their traditional revenues. In recent times Australia's telcos have finally warmed to the idea of letting customers make standard voice calls via data networks, embracing Voice over LTE and Voice over WiFi.

Telstra introduced VoWiFi in late 2016, initially for Samsung's Galaxy S6 but it's expanding to the S7 and S8 as well as the iPhone 6 and more recent Apple smartphones. iPhone owners will need to update to the latest version of iOS, which is accompanied by a carrier settings update which adds the WiFi Calling option under the Phone/ Settings menu.

VoWiFi can seamlessly transfer between Telstra's mobile network and WiFi, even while the call is in progress, making it a practical alternative to in-home mobile boosters which telcos tend to frown upon. Thankfully VoWiFi doesn't rely on your WiFi network running off a Telstra fixed line broadband connection, it should work with any ISP, but data used by calls is unmetered over Telstra connections.

Unfortunately VoWiFi isn't as flexible as some people might like. Telstra's FAQ says you can use it on an iPhone in Aeroplane Mode with WiFi switched on, but in practice it doesn't seem to work – with the iPhone's dialler app telling you that you need to disable Aeroplane Mode to place a call. (UPDATE: Telstra tells me you can only make calls in Aeroplane Mode on Samsung phones, not Apple phones).

There's no easy way to force you phone to use VoWiFi, it only kicks in when the mobile phone signal isn't up to the task. It works with the 900,000 Telstra Air hotspots across Australia, although most would still be within range of the mobile voice network. The expansion of VoWiFi comes as Telstra builds more mobile towers in regional Australia while fighting a push for it to offer regional domestic roaming deals to competitors.

Optus added VoWiFi support for the Samsung Galaxy S7 and S7 Edge back in January, although it's previously offered the WiFi Talk app which lets you make voice calls but isn't as tightly integrated with your phone as VoWiFi. Optus previously scrapped its Home Zone femtocell, a decision which made for some very unhappy customers.

Are you waiting for your telco to support VoWiFi on your handset? When would it save the day?