You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: Can you please help me to make a reservation from ORD to DCA?

ASSISTANT: Sure. Let me know your travelling dates.

USER: My depart and return dates are on Dec 24 and Dec 26.

ASSISTANT: Do you have any class preference?

USER: No.

ASSISTANT: Is there any connection limit?

USER: I need a direct flight.

ASSISTANT: Can I know your name?

USER: My name is Robert Hall.

ASSISTANT: Sorry, no flights found for your travelling dates.

USER: Ok, not a problem.

ASSISTANT: Thank you.

USER: Thank you.