Standard cut/paste reply to a 'missing socket' topic would be ...
Sometimes there is no wall box, just a trailing cable. The cable could be hidden within, or behind, furniture. Occasionally only a very short stub of wire is left behind often hidden within a blanked-off fitting. A few examples of the kind of things to look for are in the images below from past topics.
https://community.virginmedia.com/t5/QuickStart-set-up-and/Untidy-installation/m-p/5433266#M239199
https://community.virginmedia.com/t5/QuickStart-set-up-and/Reconfigure-my-setup/m-p/5434572#M239308
https://community.virginmedia.com/t5/QuickStart-set-up-and/Diamond-cable-wall-socket/m-p/5430136#M238904
https://community.virginmedia.com/t5/QuickStart-set-up-and/First-installation-and-flashing-green-light/m-p/5434785#M239339
https://community.virginmedia.com/t5/QuickStart-set-up-and/No-virgin-media-wall-socket/m-p/5395697#M235740
A wall box may be branded with the logos of an old cable TV company (not VM). Past occupiers of your property may have removed the cable and sometimes they are removed by other installers, such as satellite TV techs.
If your flat has been recently refurbished, VM cables are often ripped out as they are fairly bulky and ugly to look at. Some flats have a 'media panel' type of connection containing various connections (satellite, telephone etc.) do you have anything like that?
If you have a cable/plug trailing from the wall, you may need a coupler adapter to join two plugs together
https://www.diy.com/departments/slx-coaxial-connector-19mm/5028422001905_BQ.prd
Also available from the likes of Screwfix, Toolstation etc.
If you have a plastic omnibox outside on the wall (where the VM cable comes in from the street) see if you can trace any wires from that into your home. The wall box will look something like these
https://www.ispreview.co.uk/wp-content/gallery/2019-article-illustrations/virgin_media_external_wall_box.jpg
(styles and colours may vary and branding may be non-VM (such as former cable TV companies).
If no luck with any of the above, you will have to wait for the tech visit to get one installed.