You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Rachel Nelson.

ASSISTANT: Rachel Nelson, how may I assist you today?

USER: I am looking for a flight from DEN to OAK, can you please help me in booking a flight ticket?

ASSISTANT: Please help me with your planned travel dates.

USER: My travelling dates are May 19 and May 21.

ASSISTANT: Please let me know whether you need a direct or connecting flight?

USER: I need a connecting flight.

ASSISTANT: Please let me know with your class preference.

USER: I am fine with any class.

ASSISTANT: Please help me with your depart and return time.

USER: My departure time is afternoon.

ASSISTANT: Do you have any other preferences in your journey?

USER: No.

ASSISTANT: I am sorry to inform you that there are no active flights.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for reaching us. Have a great day.