Ask the agent via 191 to force the phone via sending an OTA configuration update that should provision your phone for Calling Over WiFi.
Other options to also try are >
"Register for Vodafone Wi-Fi Calling
Text the word CALLING to 97888
This is a free text which will add the service to your account
You should receive the following confirmation text:
Thanks. We’ll add Wi-Fi Calling to your account in the next 24 hours and will let you know when you’re all set up.
If you’d like to discuss this with us, or if you have any other issues, you can find more info here or contact us
Once you receive the confirmation text, switch on Wi-Fi Calling in your settings
Go to Settings, scroll down and choose the Application icon
Choose Phone and scroll down until you see Wi-Fi Calling – select the box beside this option
A pop-up will appear asking you to confirm if you want to enable Wi-Fi Calling – tap OK"
Make sure Calling Over Wi-Fi is turned on in your myvodafone.
Calling Over Wi-Fi will only activate when there is no network connection. Test by activating Flight Mode on your phone.
Vodafone do have a help page located here https://deviceguides.vodafone.co.uk/?topic=turn-wi-fi-calling-on-or-off
But also have a disclaimer which says " All these phones support both WiFi and 4G Calling when bought from us. Please note that phones bought from other UK network providers and third parties are unlikely to support Vodafone WiFi and 4G Calling "
I see you've bought from two Amazon sellers.
One may deal with grey imports which maybe why one has the facility and the other hasn't.
Current Phone >
Samsung Galaxy s²⁴ Ultra 512gb.
