My wife and I were being annoyed by robocalls. Saw something about Nomorobo and signed up for it. It's free for landlines (which all we needed). The way it works requires the phone to ring once, but before it can ring again Nomorobo figures out it's a robocall and intercepts it. So the ring-once is still a bit annoying, but at least you don't have to pause the movie, move the cat out of your lap, and get up to answer the phone, only to find it's robo.
So we've been happy with it; only the occasional call has been getting through.
But this morning two calls got through, one was even masked by seeming to come from someone in our telephone exchange (at least if we still had telephone exchanges). So I wonder whether the robocall people have started to figure out Nomorobo's algorithms and begun to change to counter them?