I have a Pixel 7 model GVU6C running Graphene OS. I notice that whenever I make / recieve a call it goes down to 3g. Despite there being 4g service in the area. This implies to me that the phone does not support VoLTE. My carrier is Optus in Australia. I did speak to them and they weren't very helpful but basically tried to assure me that my phone can make calls on 4g if it wants to (but couldn't explain why it always does it on 3g and why disabling 3g makes calls fail). Optus themselves do sell a Pixel 7 so I have to assume the device is supported on their network. Optus also told me that the plan im on is too old to support 5g, but I am unsure if a lack of VoLTE is related to this.
switching on 4g only mode renders the phone unable to make / receive calls. Wifi calling also does not work (despite it being an option in the settings menu)
the menu at
*#*#4636#*#* does show "volte provisioned" as well as "wifi calling provisioned" switched on however both are grayed out. I read this is because the carrier controls them but they do appear to be on.
Interestingly it also shows "voice network type: LTE" however whenever a call is actually made this switches to UMTS (3g)
The phone is using a physical sim that I just put in from my previous phone
I know VoLTE on custom roms is a bit of a meme but 3g networks will be shutting down within the lifetime of this phone so it is kind of important.
Thanks in advance for any help