I just don't answer calls that I do not recognize and if they do not leave a message, I do not call back.

that Call Blocker has an off switch in case you are in a bit of an evil mood

My wife (bless her) made the mistake of giving to one of those police or fire fighter charities that calls. Since then they have been relentless. She a sweetheart but, even she finally gave them a piece of her mind. We'll never give again and that's what she told them. That slowed them down somewhat. I wonder if those companies know the damage they are doing.

I let my husband answer he has a arsenal of ammo like thank you calling J's massage palor we try not to rub you the wrong way.
Inflatable alter boy rentals
You reach the drug traffickers hotline.
And many more.

IMO, the longer you can keep them on the phone, the more it costs them. If nothing else, just leave the phone off the hook until they hang up. But even better-- engage them and waste their time. If enough people would do that it would drive the cost of telemarketing through the roof and would remove the profit motive.

If your Android is rooted, Root Call Blocker is an awesome app.