Ultimately, the only thing that will make these scum stop is to make their business model unworkable. I ALWAYS answer the phone (hey, i AM paying for it...), and if it is someone violating the National Do-Not-Call Registry, it is GAME ON! I waste as much of their time as possible, expressing interest, giving bogus information if asked, and generally doing anything I can think of to cost them money, including setting up appointments, getting them to send me something, etc. (depends on what type of scum is calling - use your imagination - you'll find that with practice you will improve at ruining their day...). Do you really want to STOP them, or just pass them on to the next poor victim...?
Install a call blocker and white list your friends. A legit caller will leave a message. These folks didn't. Even though I have free cell service I still lose credits for incoming calls. Problem solved. If every one did this the problem would stop
Tacoma, WA ohhh ok I know noo one in this area so guess what I don't answer...that is the way it has been ..and will continue...don't recognize I'm not answering...even those 'private callers' not answering them either............ keep em' coming may have to not have a phone soon...so tired of it all..................................