You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Steven Carter.

ASSISTANT: How can I help you?

USER: I am planning to visit Denver, will you help me in booking the flight ticket from IAH to DEN?

ASSISTANT: Sure, May I know your departure and arrival dates?

USER: My preferable journey dates are Aug 18 and Aug 20.

ASSISTANT: Do you have any specifications?

USER: I need a flight with single stop over and my return time must be in evening.

ASSISTANT: Sorry, there are no flights found on your trip dates.

USER: Not an issue. Thank you for your service.

ASSISTANT: Thank you for reaching us.