You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I assist you?

USER: Please provide a ticket from Washington DC-DCA to Houston, TX-HOU.

ASSISTANT: Sure, I will help you in booking your flight ticket. May I know your travel dates?

USER: Ok. My travel dates are from 09/13 to 09/15.

ASSISTANT: May I know your name?

USER: My name is Stephen Johnson.

ASSISTANT: Johnson, please wait for a while.

USER: Ok.

ASSISTANT: Sorry Johnson, there is no flight available on your preferred travel dates.

USER: Thank you.

ASSISTANT: You are most welcome and have a nice day.