In a new relationship you're still getting to know each other so of course you'll be doing a lot of flirting around and talking about physical topics because you're just starting to get comfortable which each other. I wouldn't worry about it, I mean that is cool you can talk on the phone. 3-4 hrs might be a little overkill. You can easily think of questions to make the subject go in a different direction, like ask her about her favorites, or where she would like to go on vacation, or situational questions like "what would you do if..." or "which would be worse...," You'll have plenty of time to talk serious.