Is the only real solution to only accept calls from a phone number whitelist? The regulatory problem I can't work out how to solve is that of foreign companies

Is the only real solution to only accept calls from a phone number whitelist? The regulatory problem I can't work out how to solve is that of foreign companies attempting to scam people, e.g. the variations on "I'm calling from Microsoft, your computer has a virus..." If you can only take action against companies based in your country, what's the next step?