Sometimes it is really hard to feel bad for them. I got a call from this woman selling some vacation package. I asked her to tell me more, and after about a minute or so, I told her I am not interested. She went mad, accusing me of wasting her precious time and that time is money for her etc etc. How am I supposed to make a decision without even knowing what she is selling? I wasn't even trying to mess with her, was genuinely interested in what she was selling. And this was an unsolicited call too.

This definitely works - https://www.donotcall.gov/ not always though