You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Donna Nelson.

ASSISTANT: How can I help you at this moment?

USER: I would like to book a ticket from DCA to OAK, can you please help?

ASSISTANT: Sure, I can help you in booking flight ticket. Could you please mention your travel dates for booking flight ticket?

USER: I am travelling on these dates 07/28 and 07/30.

ASSISTANT: Ok, please wait a moment.

USER: Sure. Ok no problem, thank you for your services.

ASSISTANT: Sorry no flights available in this route as per your requested dates.

USER: Thank you for your services.

ASSISTANT: Thank you for reaching us, have a nice day.