You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: I am looking to book a flight ticket from HOU to DCA. Can you help me for that?

ASSISTANT: Sure, I am here to help you. May I know your travel dates please?

USER: My travelling dates are Apr 11 and Apr 13.

ASSISTANT: Ok, do you have any specifications?

USER: My depart time is afternoon.

ASSISTANT: Ok, hold on for a moment. Let me check the best available flight for you.

USER: Make sure that my class should be business.

ASSISTANT: Ok, may I know your name please?

USER: My name is Rachel Williams.

ASSISTANT: Sorry Rachel Williams, there are no flights available on your requested dates.

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

ASSISTANT: Welcome, thank you for choosing us. Have a great day.