Airplane mode when not expecting a call. Many of these services will only call "hot" numbers - numbers that pick up/give some interaction. Hitting "decline cal

Airplane mode when not expecting a call. Many of these services will only call "hot" numbers - numbers that pick up/give some interaction. Hitting "decline call" actually gives them an indication the line is hot, since the call went to VM earlier than if it had timed out, and will lead to more calls. So I let the calls ring until the other side ends the call. Having the spam call ringing is annoying though, so I've taken to leaving my phone in airplane mode if I'm not expecting a call. (Most people communicate via email or Signal with me anyways) In my experience if you leave your phone in airplane mode when not expecting calls for a week or so, it'll drastically cut down on the robocalls.