I think you hit on something here. In phone situations where I'm able to help, I've found them to be generally positive, even if the person started off a little angry. It's the ones where you're stuck between company policy and an angry customer who also happens to be in the right where it really grinds you down. That said, there's only so much you can take of people coming in angry at you and having to cheer every single one of them up.