Welcome to our Community and thanks so much for your first post - sorry to understand that you've been getting some unwanted calls recently. All providers have seen an increase of scam/spam calls over the last few months; we assure you that we're doing what we can in the background to try and reduce the amount that get to you however, with new scams and numbers (including number spoofing) this is a difficult task.
We do have a dedicated help page about Nuisance Calls which may help you out.
For calls that look like they're coming from an international number such as in your example, this has a special name - Wangiri. You can read more about that one here
We've had several scam calls recently from numbers beginning 001, which are obviously fake phone numbers. Why don't Virgin Media block these calls?
These calls cannot be blocked for several reasons. These calls originate from abroad via the internet through many possible gateways. Because the system we use is analogue, there are no possibilities for adding security to authenticate the incoming number.
These scammers can also fake ANY number. As explained above, the lack of security means they can clone numbers of genuine businesses & residential lines as well as unused ones.