听下面一段较长对话，回答以下小题。
Why does David want to speak to Mike?
听力原文：
W: Hello, Helen Smith speaking. Can I help you?
M: Hello, this is David. Could I speak to Mike, please?
W: I’m afraid he’s not available at the moment. Would you leave a message?
M: Yes. I’m calling to cancel a meeting we scheduled for this afternoon.
W: Okay. Let me take this down. Could I have your name again?
M: Certainly. It’s David Stone.
What do we know about the speakers?