See post below from yesterday for info
https://community.virginmedia.com/t5/Home-Phone/No-link-to-the-hub/td-p/4785562
I believe it may depend on each particular VM area as to whether you can opt in to it or wait until it is rolled out by VM to your area.
Check out the info on the pages below
https://www.virginmedia.com/help/home-phone/virginphone/switchover
https://www.virginmedia.com/help/home-phone/virginphone#whatishappening
which highlight some of the limitations of a phone connection from the back of the VM hub (in particular issues with the landline potentially not being operational depending on the status of the hub and also connecting other legacy equipment such as burglar alarms, care devices etc.)