Yep, he's right. Be careful not to overcall. That's why they usually hang up. Soft, subtle calling is almost always the right thing to do.

Sometimes if they hang up, I turn my head away from them and call very soft. This makes 'em think I'm going away and not very interested. THis works about 40% of the time. Once they hang up, you're usually screwed. Back out carefully and try at him at a completely different angle, or sneak back in a couple hours-and start over very quietly and casually.