You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you today?

USER: My name is Nancy Perez. I want to attend a seminar in Philadelphia, can you book a ticket with price under 500?

ASSISTANT: Sure, please help me with your travelling dates please?

USER: Sure, my travelling dates will be 11/17 and 11/19.

ASSISTANT: Ok, let me know with your airport codes please?

USER: Yes, I would like to travel from DCA to PHL.

ASSISTANT: Ok, please wait I will get back to you.

USER: Ok.

ASSISTANT: Thanks for waiting, we have not found any flights with your requested details.

USER: Ok, no issue. Thank you.

ASSISTANT: Thanks for choosing us.