You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am planning to visit Oakland for my sisters marriage, can you please help me in booking a flight ticket from DCA?

ASSISTANT: Sure, may I know your trip dates please?

USER: Sure, my trip dates are July 28 and July 30.

ASSISTANT: Do you have any other requirements?

USER: Yes, I prefer economy class with 1 stop over in between my journey.

ASSISTANT: Can I know your name please?

USER: Janet Campbell here.

ASSISTANT: Sorry, we regret to inform you that there is no flight available as per your request.

USER: Make sure my depart time should be during afternoon. That's ok, not an issue. Anyways thank you for checking.

ASSISTANT: Most welcome.