“Call Voicemail” missing from Phone app

I have successfully transferred all my settings from my old iPhone SE (1st generation) to my new iphone SE (2nd generation) using the phone to phone transfer process in iOS 14 but have one niggle. I have Vodafone Voicemail set up and can access it by dialling 121. However, in the iPhone Phone App the fifth option at the bottom labelled “Voicemail” shows “No Voicemail” instead of “Call Voicemail” as on my previous iPhone. There is no Set-Up shown and only “Greeting” to re-record my outgoing message is there (top left).

How can I get “Call Voicemail” to show on the Voicemail tab?

Thanks for your help.