You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you at present?

USER: I want to book a ticket from SFO to DFW. Could you book a ticket?

ASSISTANT: Sure, can I know your good name please?

USER: I am Melissa Lopez.

ASSISTANT:  When you are willing to travel?

USER: Depart date is June, 28 and return by June, 30.

ASSISTANT: Do you need direct flight or connecting flight?

USER: I would prefer connecting flight.

ASSISTANT:  Would you let us know if you have any other preferences?

USER: I prefer business class.

ASSISTANT: Sorry to say that, there are no flights available on the routes of your journey.

USER: Thanks.

ASSISTANT: Thank you for choosing us.