I had been “sorta” doing that but I get so many on my cell from numbers I don’t know that I usually just answer but don’t say anything and wait until they speak. Most just hang up. But from now on anonymous and unknown will be at the top of my ignore list.
Download the Hiya app on your cell phone. It shows up on your screen and tells you if a call is spam, a telemarketer, and if others have reported it already. I’ve recommended it too many people and everybody is quite happy with it.
I have my iPhone set to accept calls from contacts only. Wish I could do that for the landline.
And add those numbers to your “block” list.
Because I sometimes get calls out of the blue from folks I've never met, referrals from prior clients, I can't just ignore cell calls. But I do not say hello for the first ten seconds or so. That causes the robocalls to hang up and move on and live people to say "hello"?