You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I guide you today?

USER: Yes, can you help me to book a flight ticket to DCA and my origin airport is OAK, can you help me with it?

ASSISTANT: Ok, could you please help me with your dates of journey?

USER: Ok, I want to start my journey on 11/20 and return date is 11/23.

ASSISTANT: Sure, may I know your name please for booking purpose?

USER: Sure, my name is David Carter.

ASSISTANT: Sorry Carter, there are no flights found as per your travelling details.

USER: That's ok, I will plan some other day.

ASSISTANT: Thank you for contacting us.

USER: Anyways thank you for assisting me.