I called back: "the number you have dialed is not in service please check the number and try again."
I take it that if it's a legitimate business someone would answer. So I'm blocking this number as they have called back many times not leaving a message. They are now blocked!
They have called several times but we let all calls go to voice mail if we don't know who's calling. The only message they leave is a recorded message that says "good bye".