One trick is to answer the call but don’t say a word and make no sound (go on mute if you can).
Once they realize there is no response (computer or human on their end), the call is disconnected and the number is flagged in their data base as “inactive” and they stop calling it. If it rolls to voicemail, it is still considered “active”.
Once I started doing that, my robo and spam calls dropped to nearly zero.
