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...?
Panasonic Phone model KX-TGF342
Blocks 250 phone numbers can be purchased online, walmart.Com and other online stores. Very easy to use has a button on the base and on the hand held units that reads Block Call you can also very easily enter a number manually not complicated at all.