You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Andrew Lee.

ASSISTANT: How may I aid you today?

USER: I am planning to visit Olympic National Park at Washington, could you please help me with booking a flight ticket from ATL to DCA?

ASSISTANT: Sure, I will help you with that. Can I know your travelling dates please?

USER: I would like to depart on Feb 10th and return on Feb 12th.

ASSISTANT: Ok, do you have any class preference?

USER: I am comfortable with any class. And make sure that my depart time is evening.

ASSISTANT: Do you have any airline preference?

USER: No, but I need a connecting flight.

ASSISTANT: Please wait a moment to check the flights on your route.

USER: Sure, take your time.

ASSISTANT: We regret to inform you that, there are no flights available with your requested departure time.

USER: Ok, not an issue. Anyways, thank you for the information.

ASSISTANT: Thank you for reaching to our services, hope you have a great day.