You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: Can you book a flight ticket from DFW to HOU?

ASSISTANT: Sure, I am here to help you with that. Can I know your planned trip dates?

USER: Apr, 4 and Apr, 6 are my trip dates.

ASSISTANT: May I know your name?

USER: Karen Clark here.

ASSISTANT: Do you have any other requirements?

USER: I need to travel in connecting flight with business class.

ASSISTANT: Ok, wait for a minute.

USER: Sure.

ASSISTANT: Sorry to say that, there are no flights available based on your travelling dates.

USER: That's ok, thank you.

ASSISTANT: Thank you for approaching us.