Who am I being ruder to now?

One of the biggest, most exciting shake-ups from my childhood was when our parents finally gave in and let us get call-waiting on our phone. We were definitely the last people on our block to spare people from hearing that annoying—and now virtually extinct—sound of the busy signal. But one of the rules my mother insisted we follow with this newfangled technology was that whomever we were talking to first was the priority conversation, and anyone who beeped in had to be told, "I'm sorry, I'm...