And telemarketers almost never leave messages, so that eliminates them.
What gets me is having to change my phone habits so radically, and even buy a second phone line just to take 99% bogus calls I get from my public phone number that's posted on the net. I think there was a thread where people asked why nothing is done about these calls, and someone mentioned that politicians all use junk calls for their own campaigns, so they don't want to do anything that would affect their right to bombard us with robo calls every election season. Which makes a lot of sense when you think about it.