Firstly - It is appalling that our governments allow this to go on. They could, if they wanted to, block scam calls from foreign call centers.
I'm on the national do not call register but this does not deter foreign call centers.
We need to apply political pressure.
Secondly - *** If I don't recognize a number then I may pick up the phone but say nothing. ****
Call centers robo call and only put the call through to an operator once they hear a voice.
If you don't say anything then they just hang up.
Whereas a legitimate caller will speak and you can then answer them.
To protect your PC, you should have two user logins for yourself. One with Admin privileges and the other as a regular use.
Only login as the Admin if you need to install software. If you aren't logged in as an Admin then hackers, who get into your system, don't either.