One morning a few years ago as I was getting ready to get in the shower a spam call comes in to my landline. I don’t remember the exact bogosity but I think it was the ol’ your computer has a virus thing. When he asks for payment I say I will get my credit card but it is down in my car and will he wait? He agrees and damned if he wasn’t still waiting for me when I got out of the shower 20 minutes later.
My personal best was 2 hours and 10 minutes before it was me that got sick of playing them.
After that I put the "This Number Out of Service" tones (http://www.k3pgp.org/telezap.htm) on my answering message. That knocked out a lot of the spam diallers.
Usually I don't answer any number that's not on my contacts list, and let them go to voice-mail. If they really need me, they'll leave a message.
I do that too. I even got an app that does this automatically. I just get a silent notification afterwards, it's great. It's very rare that I'm expecting a call from someone I don't know already, so there's no problem.
Unfortunately, not everyone has this privilege -- people who work with sales, for instance.
You are a hero. We need a personally secretary app that would identify spam calls and keep them waiting forever, plying To Elise music in the background.