The carrier claims to have already enabled VoLTE, and sent warning SMS and email based on how my phone connects. On the network page in phone settings I have mobile data enabled, 4g calling enabled, prefferred network 4G etc. The status bar shows a 4G icon when I have mobile data enabled). I’m not sure what mroe I can do on my phone to suggest is use VoLTE.
This is something that has widespread public alarm in Australia and the shutdown was delayed a year as a result, so I’m fairly confident that the carrier is correct.
It’s possible that if I changed to a different network provider (Australia has three networks and many, many resellers) that would work, at least in the major cities. But the reason I chose the carrier I did is to get coverage in rural areas. Sadly they’re also the carrier most people who are having VoLTE issues are using (ie, the other two carriers have fewer people reporting issues. Which suggests that newer Fairphones might have the same issue, so I may have to wait until after the 3G shutdown to be sure other FP users are correctly reporting whether their phones work.
I’m using the band information from GSMArena and Telstras “bands and frequencies” from this web page: Our Coverage & Rollout Maps - Telstra which is why I thought it would work. Telstra use bands 3,7,28 and 3+ uses 3,7 (plus many others).