You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I need to travel DCA and OAK, can you please reserve flight ticket?

ASSISTANT: Sure, I can help you with that. May I know your travel dates please?

USER: My travelling dates are Oct,04 and Oct,06.

ASSISTANT: May I know which are your source and destination in the given codes?

USER: My source code is DCA and destination airport code is OAK.

ASSISTANT: Fine, do you prefer direct or single connected flight?

USER: I need single connecting flight, that's it.

ASSISTANT: Please let me know if you have any other specifications.

USER: No.

ASSISTANT: Can I have your good name please?

USER: Myself Mark Jones.

ASSISTANT: Sorry, no flights available on those dates with your given details.

USER: That's ok, thank you for your great service.

ASSISTANT: Thank you for choosing us.