I've been getting quite a few of these recently. I strung the first couple along before asking them if their mother knew that their child was a scammer and a thief and whether she'd be proud of what they're doing, but that didn't put them off and now, even though I tell them I know it's a scam and I'm not going to download their software, they *still* keep trying and even call back!
Unfortunately there's nothing I can do short of blocking international calls (which I don't want to do as it's my business phone line) and the TPS is as much use as a chocolate fireguard for stopping them.
Virgin did say I could contact a bunch of people calling themselves the "Call Prevention Registry", but they want £40 a year and all they do is "supply more than 1,500 data houses throughout the UK and overseas with our Do-Not-Call lists" which is only any good if the scammers actually paid any attention to such lists.
They can also (for sixty quid) supply you with "The All in One Call Blocker" which is a gizmo that you plug into your phone line and which will store a scammer's number and block it in future, but that only works if they haven't witheld their number and it's not an international call. It also claims it can block international calls, but I can get Virgin to do that already and, as I've said, I don't want to do that on my business line