I don't answer when I don't recognize the number, but I receive so many calls from this number, which is obviously a robo call, that it has become a problem.
These people call every day and sometimes several times a day. I have hit the ignore button, but quite obviously this alerts them as yoda 1725 states- "this alerts them that they have reached an active no." I will check with the phone co. to see if they have a call blocker for cell phones.
I don't have a call blocker , but, I created a 'contact' on my phone named 'ASSHOOLES', and added this number to it. It pops up I already know who they are !!! THANKS.