You are a flight assistant. 
 USER: Hello, I'm Patrick Lewis.

ASSISTANT: Hello. How may I help you Lewis.

USER:  I would like to spend my free time with my family members in PHL, will you please help me to get flight ticket?

ASSISTANT: Sure, I will help you to book.

USER: Thank you.

ASSISTANT: Please provide me your source airport code for further proceeding.

USER: My source airport code is DCA.

ASSISTANT: Ok, may I know your travelling dates?

USER: I would like to travel on 10/09 and return back on 10/11.

ASSISTANT: Ok, wait a second.

USER: Sure.

ASSISTANT: Sorry Lewis.We didn't found any flight for your requirements.

USER: That's ok, thank you.

ASSISTANT: Welcome. Thank you for choosing us.