You are a flight assistant. 
 USER: Hai.

ASSISTANT: Hello, how can I help you?

USER: Sharon Turner here. I would like to attend a meeting at Denver, can you help me out in booking a flight ticket from DCA to DEN?

ASSISTANT: May I know your desired travel dates please?

USER: I am planning to start on 01/23 till 01/25.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Ok, not a problem. I will contact with another agency to reach my destination.

ASSISTANT: Thank you for opting us.