You are a flight assistant. 
 USER: Hello, Margaret Taylor here.

ASSISTANT: Hello, do you need any help from us?

USER: I planned to attend for a meeting in AUS, can you please help me to book a flight ticket from DCA?

ASSISTANT: Sure, can you please tell me your trip dates?

USER: I planned to start on 09/18 and return back on 09/20.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there is no flight on your requested travelling dates.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.