You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I am Carolyn White want to visit IAH, can you book a ticket from DCA?

ASSISTANT: Sure, may I know your dates of journey please?

USER: Sure, my travelling dates will be 08/17 and 08/19.

ASSISTANT: Ok, wait for a moment please.

USER: Ok.

ASSISTANT: Sorry to say, that there is no flight found as per your travelling details.

USER: That's ok, thank you.

ASSISTANT: You are welcome.