You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Can you please help me to book a flight from DCA to ORD?

ASSISTANT: Sure, could I have your trip dates, please?

USER: I want to travel on Sept 21 and need to return on Sept 23.

ASSISTANT: Do you have any specifications?

USER: I need a direct flight.

ASSISTANT: On what name, do I need to reserve the ticket?

USER: I am Anna Clark.

ASSISTANT: Sorry, no flights are available as per your requirements.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for opting us.