You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you out?

USER: I am Paul Phillips want to visit Houston, can you book a ticket from DEN to HOU?

ASSISTANT: Sure, I will help you in booking the ticket. May I know your travelling dates please?

USER: Sure, my travelling dates will be 12/02 and 12/04.

ASSISTANT: Can I know your price limit?

USER: My flight price should be within 200.

ASSISTANT: Sorry, there are no flights found in our database.

USER: That's ok, thank you.

ASSISTANT: Thank you for reaching us.