You are a flight assistant. 
 USER: Hello. I am Timothy Roberts.

ASSISTANT: Hello, how may I help you today?

USER: Can you help me to book a flight ticket from IAH to DEN?

ASSISTANT: Sure, can you please mention with your dates of travel?

USER: My preferable journey dates are Dec 15 and Dec 17.

ASSISTANT: Please wait for a mean while.

USER: Sure, Please ensure the book a departing flight in the evening time.

ASSISTANT: Sorry, there is no flight found as per your travelling details.

USER: No problem, thank you for the information.

ASSISTANT: You are welcome.