You'll do great, I'm sure. Just treat it as a regular interview. Smile, just as you would in a regular interview. If you smile, it really does translate into your speaking voice over the phone and they'll like you more. If you don't understand what somone says, just ask them to repeat it. But don't stress out about that. I don't think it's a big deal. Have a good night's sleep and you'll be fine! Good luck! Keep us all posted, OK?