I've never had to. When someone asked for Mrs (my maiden name), and I said I was Ms, they hung up on me. When a real estate agent asked if we were selling our house, or if anyone around us was, I said that the neighbors were too shy to talk to us. Another hang up. I think the only time I've been unpleasant was when someone trolled WHOIS info to call about a website, and I told them how many policies they'd broken.