For fluff, it seems to me it just needs good listening skills, and try to put yourself in their shoes. You might want to emphasize your sympathy for their crappy travel experiences, and that can make them feel listened to and sympathized with.

The higher tone of voice, that's a really good question. I had that too for a long time. It's mainly a stress reaction. When I was having surgery, back in '84, I heard my voice which had gotten very high-pitched due to fear and anxiety. And people were remarking about it, which made it worse. I think if you keep your attention on them, your tone of voice may change more toward natural. For me, it took its own time. I'm not sure if it's gone for good, but I think it mostly is. Good luck, hope it works out well for you.