You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Justin Gonzalez. Can you help me to book a flight with 500 price limit?

ASSISTANT: Ok, may I know your travelling dates?

USER: My travelling dates are 03/05 and 03/07.

ASSISTANT: May I know your travelling airport codes?

USER: My preferable airport codes are DCA and DTW.

ASSISTANT: Sorry, there is no flight is available for you.

USER: Ok, no issues. Thank you for your time.

ASSISTANT: Thank you for choosing us, have a nice day.