Thank you for your post and welcome to the forums.
As you can appreciate on the forums/community we provide information and advice based around what is put towards us. I can only assume from your post that you are wondering why you have not received a letter for the switchover - if you have not received any communication on this, it would be that this isn't ready to be rolled out in your area yet. All information on this can be found through this link: https://community.virginmedia.com/t5/Virgin-Phone-Switchover/gh-p/Switchover
That link would outline all details relating to the switchover and provide all information needed.
If there is something else - please just let us know, as we're more than happy to help 🙂