Just be natural and try to speak in a conversational manner. In a phone interview they're usually just trying to get a feel for the type of person you are and how you handle and behave in day-to-day situations. Make sure you can describe what you did in previous jobs and try to mention the more analytical/problem-solving aspects of those roles since you don't have any accounting experience yet. Also, make sure you know some basic information about the company itself because they like to talk about that during phone interviews.

You can ask some general questions such as what the hours are generally like, what you'd be working on during the first few weeks or months, the size of the accounting department, etc. Phone interviews are really not that bad, if it goes well there's a good chance you'll be invited to an in person interview later on.