Turn on your phone's and carrier's free call-blocking tools
Added
Use both layers: your phone's built-in setting (iPhone 'Silence Unknown Callers', Google Pixel 'Call Screen', Samsung Smart Call) and your carrier's tool (AT&T ActiveArmor, T-Mobile Scam Shield, Verizon Call Filter). Handy for drivers who need to keep the phone free for real calls. You can opt out if wanted calls get blocked.
The result
Result: FCC: phone companies may block suspicious calls and many offer enrollment or apps at little or no cost; a blocked call may go to voicemail, ring once, or not notify you at all.
Source
FCC: Call Blocking Tools and Resources (opens the original source in a new tab). Check it for the latest numbers before you act.