Never trust an incoming number. All incoming numbers to your phones can currently be easily "spoofed". Scammers do this due to the way the UK telephone network has been built over a number of decades. Scammers spoof emergency services, HMRC, Banks. They lure you in by "google the number I am calling from to verify me".
Good news is Ofcom is working with providers to mitigate this long term and hopefully measures will be implemented to prevent this in the future.
This is what is referred to as computer services fraud. The scam would likely to be as follows:
1) Fraudster directs to a website that is meant to look like a genuine virgin media website.
2) Download some remote support software, most likely AnyDesk statistically.
3) At this point the fraudster will convince you to grant remote access to your computer.
4) Fraudster connects to your computer. They will typically run either Command Prompt or Windows Event Viewer and show errors (which actually are nothing to worry about.)
5) They will then offer to fix for a fee or subscription to fake anti virus they offer.
6) They will direct you to a website where you input your card details.
7) These card details either get used or sold on the dark web for further criminality.
Unfortunately there is a strong link to these scams back to India and the international law enforcement community is trying.
Please see a recent news article
https://www.interpol.int/fr/Actualites-et-evenements/Actualites/2016/INTERPOL-operation-targeting-ph...