There is more behind this question than meets the eye.
The only possible reason for needing a VAT invoice on a residential service like VM is because you are running a business from home and wish to offset the VAT you pay on your VM services against the VAT you are obliged to charge.
If this is the case think carefully about what you are asking for. Using VM residential services for business needs is forbidden under the VM residential terms of service except in limited cases involving working at home and connecting to an employers system. VM will enforce its terms of service against you if it thinks you are in breach of them.
However you might like to read this thread from 2018 which explains the circumstances in which VM will, on application, provide a VAT invoice:
https://community.virginmedia.com/t5/Managing-Your-Account-Cable/Bill-with-VAT/td-p/3837667
As a Very Insightful Person, I'm here to share my knowledge. I don't work for Virgin Media.
Click to learn more about VIP
Use Kudos to say thanks
Mark as Helpful Answer if I've helped