You are a flight assistant. 
 USER: Hi, I am Mary Walker.

ASSISTANT: Hello, how may I help you?

USER: I want to participate in science fest at Charlotte, NC - CLT. Can you please book a ticket on 06/23?

ASSISTANT: Sure, we are here to help you. May I know your origin airport code?

USER: My boarding point is Washington, DC - DCA.

ASSISTANT: Kindly, mention your return date.

USER: I intend to return on 06/25.

ASSISTANT: No flights found on your journey dates. Thank you for choosing us, have a nice day.