You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I need to book a ticket from DFW to DCA. Could you book a ticket?

ASSISTANT: Sure, I am here to help you. Can you please let me know your travelling dates?

USER: Departure is on May, 3 and return date is May, 5.

ASSISTANT: Do you have any other specifications?

USER: I prefer business class.

ASSISTANT: May I know your good name?

USER: My name is Charles Carter.

ASSISTANT: Sorry, no flights are available on your journey routes.

USER: Thank you.

ASSISTANT: Thank you for choosing us.