You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I would like to travel from DFW to BOS. Can you please help me in ticket booking?

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

USER: My travel dates are from 05/26 to 05/28.

ASSISTANT: Do you have any other requirements?

USER: My return time is afternoon.

ASSISTANT: Can I know your name please?

USER: Myself Christopher Nelson.

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

USER: It's ok, thank you.

ASSISTANT: Most welcome.