Working in a call center, taking payments for Sprint customers who had their phone shut off due to non payment:

Man: "...I need my f**ing phone turned on now."
Me: "I'm sorry your service has been interrupted sir. I can take your payment, and get it turned on. It may take up to 2 hours."
Man: "Are you f**king incompetent? I'm a g*d d#$mn contractor and work with dynamite. If I don't have my phone on, people f**ing die!"
Me: "Ok, then I'm sure you realize how important it is that I get your payment right now, to get the process started. Can just get your - "
Man: " - Are you calling me an idiot?"
Me: "No, sir. I don't believe that is necessary."
--Long silence--
Man: "Ok. I'd like to make a payment." - in a much more pleasant tone.