@XSGeek
You have to register your phone number if it's a land line. AFAIK, mobile phones are automatically do-not-call unless you've requested calls, since you pay for incoming calls in the US.
Then when you get a call, answer and find out what they are calling themselves and why they're calling. Enter it all in the form.
Apparently, it's gotten harder to use spoofed numbers, as most seem to be the snowshoe type now.
I recommend an app called "Simple Call Blocker." Totally free.
https://apps.apple.com/us/app/simple-call-blocker/id1409872025
Then look up the incoming number on telcodata.us
https://telcodata.us/search-area-code-exchange-detail
Look up the area code and exchange, then scroll down to the 1000's block to see which company rents it out. Learn which companies keep showing up as the source of spam calls, and block their whole damn range.
@XSGeek
Blocking single numbers is fraught -- some will be "spoofed" -- ie, you're blocking the number of some different person, often someone in your neighborhood who had nothing to do with the call. Others are "snowshoe" callers, where they get a large block of numbers and keep using a different one every time they call.