So confused about WiFi calling - please help clear this up for me

[Sy13]

Hi all,

I live in an area where I need WiFi calling / VOLTE / whatever it's called on my handset. But I don't understand what is needed to guarantee this when I switch providers. I would like to buy a new phone on O2 contract but they are so pricey like that. However, my understanding was that I'd need the phone from them so the O2 firmware was installed for WiFi calling to work.

If I buy the Pixel 5 from Google direct and put an O2 Sim inside, will I get WiFi calling despite the absence of O2 firmware?
How can I (or anyone else) be certain if this will work when choosing new phones and suppliers?
The O2 site suggests that the Pixel 3XL is the most recent Google phone that supports WiFi calling. Does that mean the Pixel 5 doesn't support it or O2 don't support it without their firmware? Link: Wifi and 4G Calling | Help & Support | O2
There are a number of new phones also missing from their list: S20 FE 5G, OnePlus 7 and above etc. So does that mean you can't use WiFi calling due to firmware or those phones don't have it as a feature?

Thanks in advance for your help. To clarify, I just want to get a Pixel on a new O2 contract with WiFi calling. What's the cheapest way?

 

[ashenfie]

If the phone is supported by your wifi provider then all is good, in most cases nothing to do. No idea what firmware you think is needed.

 

[Sy13]

If the phone is supported by your wifi provider then all is good, in most cases nothing to do. No idea what firmware you think is needed.

I know when I got my Galaxy S7 years ago on Three, I bought the handset only and put my contract SIM inside. Hours later I discovered that WiFi calling wouldn't work unless I got the phone from Three because it required the Three firmware installed.

 

[ashenfie]

My phone works fine with wifi from Sky and phone from Vodafone.

 

[Sy13]

My phone works fine with wifi from Sky and phone from Vodafone.

Thanks but I'm not sure that provides definitive answers for my situation. Was your phone supplied by Vodafone? What phone is it?

Is there a resource somewhere that explicitly defines whether WiFi calling works on handsets that are SIM free rather than with certain firmware builds installed?

 

[Miss Mandy]

It's unfortunately one of those things that's hit and miss. When I had my Huawei P30 Pro with generic firmware WiFi calling would never work, but my sister's identical model she got directly from O2 worked fine.
It's worth checking the O2 community forums or places like XDA to see if other users have been able to get it working.

 

[john.hem]

For what it is worth, I have a sim free MI 9T Pro with a '3' SIM and I get VoWIFI.

 

[LV426]

I have a Sony Xperia ZX2 Compact. Bought SIM Free NOT from three.
I have a three SIM Card and SIM only contract.

WiFI Calling works simply by enabling it in the settings menu. No other firmware etc., needed.

 

[Miss Mandy]

Three usually does work fine with any handset, but the OP is asking about O2 who are not quite as good with it.

 

[quietlife]

I bought my phone direct from Samsung. No Wi-fi calling when I popped my Vodafone sim in, but a quick email to them and they sent the software to my phone. No charge or issues