We have Vodafone digital voice and have calling line identity. There are no settings available for it on the account and I don't remember needing to ask for it (we have had it for 2½ years).
There isn't much information in their support pages. It appears that it should be automatically available:
To get caller display on your landline, you need a compatible phone with a screen to show the number of the person calling you.
You might need to set the phone up to get the number to appear on the screen. Check the phone manual to find out how to do this.
Their tech support is not good. If you don't get the right agent they just read off the screen, which is what you can read on the website.
When we first had fttp installed the phone didn't work. The CSA that I dealt with insisted it was because we were using an RJ11 to RJ11 lead not a BS 6312 to RJ11 adaptor. After waiting for the adaptor to be delivered I got to speak to somebody who knew what he was talking about and identified that a firmware patch that was needed for digital voice hadn't been applied.