You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I am Kathleen Young. I am planning to book a ticket from BOS to DCA. Can you please help me out?

ASSISTANT: Fine, let me know your trip dates too.

USER: I am planning to travel on Dec 6 and return back on Dec 8.

ASSISTANT:  Is there any another specifications on your trip, so that I can arrange like that only.

USER: Yes, my depart time is evening.

ASSISTANT: Sorry to inform you, there is no flight running on your preferable dates.

USER: That's fine, thank you for your service.

ASSISTANT: Thanks for choosing us.