You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I want to book a ticket from IAH to IAD, can you help me?

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

USER: My travel dates are 09/24 and 09/26.

ASSISTANT: Do you have any other requirements?

USER: I need a direct flight.

ASSISTANT: Ok, can I know your name please?

USER: I am David Miller.

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

USER: No problem, thanks for checking.

ASSISTANT: Most welcome.