(1) Don’t answer your phone unless you recognize the number. If they want to talk to you they will leave a voicemail. Spammers usually just hang up.
(2) If they leave a voicemail and it doesn’t identify the source in a way that satisfies you, block the number.
(3) If they don’t leave a voicemail. block the number.
Easy peasy.
When you “block” a number, what does that do with the call? Does it send it directly to my voicemail? Does it provide an automated message that this phone number has been blocked? Does it just not ring? What?