Call blocking only works on legitimate numbers. Problem is, so many of these junk calls are made using spoofed caller IDs.

I get very few junk calls on my cell phone. But one that I can count on getting a couple of times a month is the Reduce your credit card interest rate scam. Some give you an opt-out prompt to have your number scrubbed. But most variations don't. So for the latter, I take the Don't bust a ball-buster's balls approach. I stay on the line and either lead the rep on using an over-the-top foreign accent and giving him/her all kinds of bogus information to totally flummox them, or I simply ask if they can promise me a rate as low as their IQ at which point the line goes stone dead! laugh