At the start of the year Telstra announced that they were going to be launching WiFi in the first half of 2016. Unfortunately the end of June came and went with no release.
However it seems that something must be on the horizon soon as the following three tweets detail support for iOS and that Telstra is a support carrier. Unfortunately the option to enable WiFi calling is not yet appearing on my iPhone 6s running iOS 9.3.3 on Telstra Pre-Paid. It's however comforting to know that we're getting the proper experience and not some half-baked app experience!
@TomFulwood VoWiFi is a feature offered by Apple. Apple has stated that to use Wi-Fi Calling, you need an 1/3— Telstra (@Telstra) July 19, 2016