One way without using the phone API directly is through Twilio using their APIs for handling DTMF tones and call forwarding. This would probably cost something

One way without using the phone API directly is through Twilio using their APIs for handling DTMF tones and call forwarding. This would probably cost something like 2 cents per minute [1] plus whatever your phone service charges (if you're just calling your existing phone) and hosting costs for your server. I was originally tempted to say you could save on this cost by hanging up on verified callers and calling them back directly, except I realized that's about the same as rejecting all calls and calling back the ones who leave meaningful voicemails / texts. I think you could get it down to 1.2 cents per minute (+server costs) if you also write a mobile app to handle all your calls via VoIP. Then you also need to factor in your cost for data if not using wi-fi. And also possibly of interest - a few days ago, Google also announced a call screening service for the Pixel [2] which transcribes call audio in real-time for you to read and possibly pick up and join the call. This one has the advantage of being able to screen out actual humans working in call centers to spam you with calls (which is less common than the robocalls in my experience). [1] https://support.twilio.com/hc/en-us/articles/223132367-How-Much-am-I-Charged-for-Call-Forwarding-with-Twilio- https://support.twilio.com/hc/en-us/articles/223132367-How-M... [2] https://www.androidpolice.com/2018/10/09/call-screen-will-let-pixel-users-see-whos-calling-want-answering/ https://www.androidpolice.com/2018/10/09/call-screen-will-le...