I keep wondering about that person on the other end of the line. Maybe they've moved to Canada fairly recently, and they've been working hard to learn the language, maybe in just a few short months they've gone from not speaking English at all to speaking it well enough to chance taking a job like this without worrying about being ridiculed, maybe they were even feeling pretty proud of the progress they've made. If so, they were certainly taught otherwise, and by a child, no less. I doubt that they'd see much humour in the lesson, though.
Yes, it is just one possible scenario, one that is as likely as not to be true. We have no way of knowing, but the thought bothers me. Although rudeness has become commonplace, I feel this incident transcends simple rudeness. It was deliberately hurtful, and it is a terrible thing to hurt someone in such a way.
Wednesday's Child, was the little book you read at Christmas called 'Talk to the Hand' by Lynne Truss, by chance? Great book, I also received it as a Christmas gift, and thoroughly enjoyed it.