I dunno how successful this is, but when I get spam called, I do what I can to reach a person and then say, "Put me on the do not call list, please!" and (possibly) as a result, I really don't get as many of these spam calls as it sounds like folks here are getting.
This WILL NOT work. The best thing you can do is sign up for the FCC DNC list. It'll take a month but then after that every legal spam call will stop.
The problem with your method is that spammers call phones just to see if they pick up. This then confirms an active number that they maintain in their lists. This can be done legally because technically calling and hanging up and never calling again (from the same number) isn't spam. So just don't answer.
Agreed, what I have done is just not answer my phone unless they are in my contact list. I also do not share my cellphone number with anyone. Seems like everyone wants it these days and the pandemic made it worse, so I have a Google Voice number for people who insist on having a number.
The only phone number that gets spam calls anymore is that Google Voice number.
For all other numbers, the calls have virtually stopped.
It does not work. I tried to take the approach of wasting their time by asking for their name and what not, but they are also getting trained to cut such calls off quite fast.