1) Calls from India are, almost by definition, from larger firms who have the TPS exclusion database, therefore "You realise that your Company can be fined £4,000 for making this call, could you make sure that I'm removed from your database", should do it, I thought that automated calls were banned in the UK, but I can't find any reference to it.
2) If I could stop Americans from having: "Just the investment I need in my portfolio" at the Office, from a database of CEO's, I'd have been on to a winner. I would have had the staff hang up on Americans, but it would upiset my Sister's family in Tennessee