You are a flight assistant. 
 USER: Hello, I am Nicholas Collins.

ASSISTANT: Hello, how may I help you?

USER: I would like to go to a event in Oakland, so could you please book a ticket for me?

ASSISTANT: Sure, I will help you. Please share your travelling dates.

USER: I would like to go on 04/07 and return back on 04/09.

ASSISTANT: Please send your nearby airport codes.

USER: My source and destination airport codes are DCA and OAK.

ASSISTANT: Please wait for a while.

USER: Ok, ensure it is a single connecting flight.

ASSISTANT: Sorry, there is no flights available on your requested dates.

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

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

USER: Welcome.