You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Patrick Hall.

ASSISTANT: Hall, how may I aid you?

USER: I want to book a ticket from DCA to LAX, hope you are help me out.

ASSISTANT: Please provide your trip dates.

USER: Ok, my trip dates are from 10/18 and 10/20.

ASSISTANT: Sorry, no flight is available on your route.

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for choosing us.