iPhone 5C - WiFi Calling. Does O2 PAYG support it?

[xtreem_neo]

Is it just the EE and Three that supports WiFi calling on my good ol' iPhone 5C?

I am thinking of moving from EE to O2 PAYG. WiFi calling is the only thing that is making me think twice. 

If O2 doesn't support WiFi calling on iPhone 5C running iOS 10.3.3, what are my options in cold dead spots around my office? 

More info

EE seemlessly switches to EE WiFiCall as soon as I enter the glass doors.  

[jonsie]

This may help if you are on contract

https://www.o2.co.uk/help/apps/o2-ask