Scam calling is a modern day plague, and although both Sky and BT offer halfway decent incoming landline call screening options, VM remain resolutely in the dark ages with no competent offer. Even Talktalk offer a moderately competent call screening service, but VM....nope, that's your and my problem.
There's no way of stopping scammers attempting to call you (because the activity is illegal even in India where most calls originate, some even use random number dialling), and because caller line ID has no security measures to stop the scammers making out the call is from any number they choose, blocking specific incoming numbers is almost totally ineffective. But there are things you can do:
You can buy a Truecall box and fit that. It'll automatically screen calls, and unless the number is in your phone book it will divert to answerphone without the handset ringing. Obviously any unknown number has to leave voicemail, but the scammers never leave voicemail, so the problem goes away, but it is expensive (£100, then £20 a year, I think). A close relative has this, and it works superbly well.
You can buy some phone handsets notably from BT or Panasonic that have a more limited form of this capability built in, and those can be quite cheap (eg BT4600 for about £40) but I can't speak from experience how easy they are to setup and how well they work, although it has very good reviews.
Or you could take your business to BT or Sky, and enable the relevant call screening capability. Again, I can't speak from experience as to how well this works, but a few enquiries in their customer forums would perhaps tell you.
