You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Frank Nelson here.

ASSISTANT: How may I help you?

USER: I would like to visit Rodin Museum with my family at Philadelphia, please help me in booking a ticket from DCA to PHL.

ASSISTANT: Ok, may I know your planned dates?

USER: My planned dates are 03/16 and 03/18.

ASSISTANT: Sorry, there is no flight for you on your preferable dates.

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

ASSISTANT: Thanks for choosing us.