We have a number of Pixel 3 and Pixel 3XLs in use in our family. They are perfectly fine for what we want to do.

BUT, Skinny are currently limiting the usefulness of these phones by playing a very long message every time we try to make a phone call, warning us that we will not be able to use them after March 2026. They must think that we a terribly slow learners, as there is no way to abort the message, or to get it to stop playing for even a day or a week. It is really very annoying. I wrote to complain, and they have "temporarily" removed the message on my phone. But while the message is there it is impossible to make a quick phone call, and often my response was that it was too inconvenient to do a phone call with the message, and just revert to text etc.

The Pixel 3 is 4G capable and does use 4G for data.
Also, in theory, it is said to be capable of VoLTE.
However it seems that a software update from Google dated June 2022 may be required. https://support.google.com/pixelphone/answer/12240791


The issue is that Pixel 3 updates ended in October 2021, before the June 2022 update needed for VoLTE.

The device also needs to have VoLTE enabled.
Skinny provided instructions to install Shizuku app and to enable toggles in the settings to enable VoLTE and WiFi calling.

This has been done on the guinea pig phone, a Pixel 3 G013A running Android 12 with Oct 2021 security update

Under settings, there is now a toggle for 4G calling that can be switched on and off.
Preferred network type is 4G.
And there is a toggle to use Wi-Fi calling.
However, if I check IMS Status by dialling *#*#4636#*#
IMS not registered, VoLTE unavailable, Voice over Wi-Fi unavailable, Video calling unavailable, UT interface unavailable
The phone will show 4G on the notification, but when a call is dialed it changes to H+
But on Settings | About phone | Sim Status Skinny, some of the stats are 
    Mobile voice network type 4G
    IMS registration state not registered


The third part is that it appears that the carrier (skinny) needs to have specific provisioning settings, either something that allows all Pixel 3 devices, or perhaps even enabling each device manually on an individual basis. Some of the reasons given online for IMS showing VoLTE unavailable are
• carrier provisioning (most frequent) - "The most frequent reason is that your mobile network operator has not enabled the VoLTE feature on your specific account or for your phone's IMEI in their system. The phone relies on carrier settings to register for the IMS (IP Multimedia Subsystem) that handles VoLTE calls."
• Regional incompatibility = Missing MBN files for local carriers missing from phones firmware
• APN settings = set to wapaccess.co.nz

I have tried contacting Skinny, but they say their settings are correct. And that their system says my phone is not VoLTE capable.

Questions:
What is stopping VoLTE from working?

Q1. Is there any way of getting the June 2022 Google update?

Q2. Is there any way to check if my device is properly set up? Or do I have to wait until April 2026 to see if it stops working?

Q3. How can I disable sim calling to force Wi-Fi calling to check it is working (without buying starlink and driving into the middle of the mountains?)

Q4. How can I check if 4G calling is working?

Q5. What do I ask Skinny specifically about the provisioning info on my device to be able to check if it is correctly set up?

What other questions should I be asking?