Contrary to what most people say, it's really hard to have a phone call only last 5-7 minutes. Take as long as you need to talk about what you want. The important thing is that when you hang up the phone, something has been set up. I've had phone calls last over an hour the first time I've called a chick, but have always made sure I had a date before I said goodbye.
As for what to say, do a search on Phone Conversation Topics. There's probably about a dozen or so that should give you enough topics to last a week. One thing that I used to do before I made a call was write down what I wanted to say. If you get stuck, look down at your paper.