You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

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

ASSISTANT: Sure, I am happy to help you with that. Can I know your planned trip dates please?

USER: I would like to depart on Feb 25th and return on Feb 27th.

ASSISTANT: Which type of class do you prefer to travel?

USER: I need a flight ticket in economy class.

ASSISTANT: Ok, how many connections do you need in between your journey?

USER: I need a connecting flight.

ASSISTANT: Ok, do you have any preference related to depart and retrun timings?

USER: Make sure that my depart time is evening.

ASSISTANT: Ok, please hold on for a minute.

USER: Sure, take your time.

ASSISTANT: I am really sorry to inform you that, there are no flights available which is departing in the evening time on the dates you have given.

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

ASSISTANT: You are welcome. Thank you for choosing our agency.