I have a Pixel 5 international version (GTT9Q) purchased from JB Hifi in Aussie, running Android 11 with the December 2020 security update. I am on the $39.99 Spark Endless Mobile Plan.

I cannot get VoLTE and 5G working

I rang up 0800 SPARK 5G for assistance and the rep mentioned I needed to get VoLTE working first before I can use 5G.

Various threads mention that for Pixel devices there should be a toggle switch to enable VoLTE under Settings -> Network and Internet -> Mobile Network -> Advanced however I do not see one.

Another issue I have noticed is that it switches to 3/3.5G whenever I am on a phone call and then switches back to 4G when the call is ended.

Anyone else on Pixel devices having similar issues? Any help would be appreciated.