I'd suggest to check your masts via the status-checker just to see if there are any issues showing.
If you get 3G/ 2G etc then you should be able to make and receive calls etc.
As a process of elimination try your sim card in another phone and then see what happens. Try another sim card in your phone if you can.
This helps to rule out the phone or sim card.
Does this happen at home or everywhere ?
Does this happen with all calls or certain contacts ?
This link has some tips and a template you can use Network-issues-initial-checks-and-template.
Customer services on 191 or Live Chat or the Vodafone Social Media Team's via Contact-us-for-account-specific-queries can check the account side of things..
Current Phone >
Samsung Galaxy s²³ Ultra 512gb Phantom Black.
