You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you at this moment?

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

ASSISTANT: Sure, please provide me your planned travel dates.

USER: Departure is Apr, 2 and return date is Apr, 4.

ASSISTANT: Do you prefer either economy or business class?

USER: I prefer to travel in economy class.

ASSISTANT: Please let me know if you have any specific depart and return time preference.

USER: I would like to return in the evening time.

ASSISTANT: Do you have any other preference?

USER: I prefer connecting flight.

ASSISTANT: May I know your name to proceed further with the booking.

USER: My name is Amy Taylor.

ASSISTANT: Sorry to inform you that we don't have any flight available for your journey.

USER: Thank you.

ASSISTANT: Thank you for checking it with us.