Put this in and it works 🙂 no matter what VF or the moderators tell you and it will work
You need to activate correct APN settings.
Settings - Connections - Mobile Networks - Access Points Names - ADD
Name - Contract WAP
APN - wap.vodafone.co.uk
Proxy - not set
Port - Not set
Username - wap
Password - wap
Server - http://www.vodafone.co.uk?cid=VOD-HOM-001
MMSC - http://mms.vodafone.co.uk/servelets/mms
MMS Proxy - 212.183.137.12
MMS Port - 8799
MCC - 234
MNC - 15
Authentication Type - PAP
APN - default
APN protocol - IPv4
APN roaming protocol- IPv4
Leave the remaining 4 settings as they are. Then press 3 dots and save the added APN
Then select the added APN and restart the phone. WI FI calling will appear once new APN embeds and gets registered.