Foward to Busy Signal

I just set the contact to always go to voicemail.

If you then have Google Voice as your voicemail, set that number as blocked. Then when the person you're blocking calls, they'll get a "this phone number is disconnected" message.

Works great for spam callers too

 

There is no way because you'd have to intercept the call before it got to VZW.

 

The only way I know of doing it is Google Voice.