Wi-Fi Calling option missing from Settings>Phone on iPhone SE, iOS 12.1.4
The Wi-Fi Calling option is missing from Settings>Phone.
My carrier, Vodafone UK, has added the function to my service but I cannot make use of it until I can turn on the option in Settings.
On instruction from Apple Support, I restored my iPhone to factory settings but this did not solve the issue.
iPhone SE, iOS 12