Wifi calling - non Optus-supplied phone

[#1]

I have a brand new Pixel 3 (model supported) but purchased from a large electronics store. Is there a way to enable wifi calling? If I understand correctly I need Optus firmware on my phone, is there any way to push this onto my handset? Seems a bit limited if I can't.

Before anyone tells me the steps in the settings etc., the options just aren't there.

[#2]

Pixel devices dont have carrier firmware as far as I am aware - its a pure Android "experence".

Do you currently get VoLTE on the device?

If not, you need to contact Optus to get it activated as its required for VoWiFi. 

[#3]

So I have just finished chat with someone who apparently enabled VoLTE on my device, though I still can't see the setting after a restart. According to this https://yescrowd.optus.com.au/t5/Network-Coverage/VoLTE-and-Wifi-Calling-for-Google-Pixel/td-p/49211... Only phones with Optus verion of Android can use Wifi Calling. Further down the thread someone says they got VoLTE to work eventually but I can't tel if their phone was Optus purchased or not.

[#4]

For those playing along at home:

Optus says here that Pixel 3 is compatible ,no caveats Ican see:

https://yescrowd.optus.com.au/t5/custom/page/page-id/tp2/VoLTE-support

But provide no instructions to turn it on.

Chat says it is enabled on my account.

But Optus says the phone must be supplied by Optus: https://www.optus.com.au/shop/support/answer/volte-coverage-networks?requestType=NormalRequest&id=16...

Regardless Chat also says Wifi Calling needs an Optus supplied device. So Optus must put someting in the firmware. Pity they can't push a setting to your phone or something.

Fail.

[#5 · Accepted solution]

Pixel 3 range does not have carrier firmware unlike all other Android phones, Optus only started selling from Pixel 3, support dont know the difference 

Is a long thread 6 pages long on here about the Pixel 3 wifi with people receiving a google supplied update in February this year and VoWiFi working. 

[#6]

Final word, I can confirm after a few extra updates (seems I didn't realise my new phone would have to go through every iteration, not just grab a cumulative update), and a day after my VoLTE being activated, my phone suggested that I might like to use WiFi calling. So I just turned it on. It is SUPER unclear from any Optus pages whether this was possible, but turns out it is. Thanks everyone who chimed in.