I am interested in buying the pixel 3a (just released in Australia) which is sold by JB Hifi or Google directly, but not by Optus. So it won't have the optus firmware. Does this mean that WiFi calling is not going to be possible on that phone?
Someone else could answer more authoratively but the Optus website is a bit ambiguous.
FWIW Wifi calling doesn't appear to depend on Optus FW, Just a valid Optus plan and compatible phone
The page shows oinly but compatible phones but the button says more compatible phones which is a bigger list.
Google 3 is on the list so that would suggest 3A is fine however its unclear if the restriction is tech or Optus applied.