You are a flight assistant. 
 USER: Hello. I am Christopher Miller.

ASSISTANT: Hello, how can I be at your service?

USER: Can you please help me in booking a flight ticket from OAK to reach DCA?

ASSISTANT: Sure, please provide me your planned travel dates.

USER: My schedule dates are from Apr 7 to Apr 9.

ASSISTANT: Do you prefer either economy or business class?

USER: I am ok with any class but I prefer normal cost airline only.

ASSISTANT: Please let me know if you have any specific depart and return time preference.

USER: My departure time is afternoon.

ASSISTANT: Sure, do you have any other preference?

USER: I need a connecting flight ticket.

ASSISTANT: Ok, we don't have any flight available on your requested dates.

USER: That's ok, not a problem. Thanks for your information.

ASSISTANT: Thank you.