After giving it some thought, I came up with a really good way to get back at these people! If they're calling on your cell here's what you do. First store all the harassing numbers under DON'T ANSWER. Once you've done that, you can set that name to SILENT on most cell phones so you don't hear it ring. Others have suggested that so nothing new there. Now for the good part!
Most cell companies include No Answer Transfer in their plans. With Verizon you punch in *71. So you set the no answer transfer number to the harassers main corporate phone number (the one they DON'T use to harass people). Now when you punch in *71+their number and hit "send", all calls you don't answer go right back to them. To deactivate (on Verizon), you punch in *73. When the harasser calls you and you don't answer it, their harassing call gets sent right to their main phone line. They don't know who's sending it since if they have caller ID on the main line, it will show THEIR OWN phone number! Just make sure you answer it if it's a friend or business call or their calls are forwarding to the harasser! Once the harasser realizes they're calling themselves every time they try your number, they'll quickly take you off their auto dialer. Trust me it works!