You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I aid you today?

USER: Can you help me to book flight ticket from DCA to OAK?

ASSISTANT: Sure, please share me your trip dates.

USER: My trip dates are Dec 17 and Dec 19.

ASSISTANT: Do you need any specifications?

USER: I need business class to travel with single connecting flight.

ASSISTANT: May I know your airlines preferences?

USER: No, I do not have any particular airline preference.

ASSISTANT: Please mention your good name.

USER: Sure, I am Eric Robinson.

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

USER: Ok, not a problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you.