For anyone in Australia using 3G and worried about the impending shutdown of Telstra's 3G network, I finally figured out how to enable VoLTE. I am with Aldi Mobile (Telstra) and have been using the "GSM/WCDMA preferred" up until today (and have needed to use dodgy hacks as mentioned in this thread of enabled/disabling speaker phone when performing a call).
So I've seen many places where you put this code in the dialer:
*#*#4636#*#*
But its VoLTe is always greyed out no matter what. I am not sure if Telstra have some whitelisting going on or what. Anyway, what finally ended up work
