I suspect the main culprit here is company policy/choice resulting in angry callers. Not to say there aren't other factors, but people generally don't call companies because they're having a good time. If Telus is anything like American TV/phone/internet companies, then I'm even more convinced of this.

edit: And if people are able to detect this and suspect they're not even talking to a human at all, it might even make verbal abuse more common.