You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you?

USER: I need to book a ticket from DCA to DFW. Could you book a ticket?

ASSISTANT: Yes, can you tell me your travelling dates?

USER: Travelling dates are Mar, 3 and Mar,5.

ASSISTANT: Do you have any other specifications?

USER: I prefer to travel in economy class.

ASSISTANT: Do you have any preferences?

USER: I need direct flight.

ASSISTANT: Give me a moment.

USER: Sure.

ASSISTANT: Sorry to inform you that there are no flights found on your requested criteria.

USER: Thank you.

ASSISTANT: Can I know your name for documentation?

USER: I am Katherine Martinez.

ASSISTANT: Sorry to inform you that there are no flights found on your requested criteria. Thank you for contacting us.