FOR YOUR AWARENESS
After noticing all of the unsatisfactory answers to the question of how to block unknown callers from ringing your phone, I decided to go into my phone app and poke around a bit. After doing that, I found a setting, in my phone app (Samsung z flip 3) that allows for blocking unknown numbers. So I'm posting this to encourage you to check your native phone app settings to see if it has that capability built in. I hope you find this helpful.
