You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Timothy Lee.

ASSISTANT: How may I help you today?

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

ASSISTANT: Sure, I am here to help you with the ticket booking. Can you please tell me your travel dates?

USER: My preferable journey dates are Nov 20 and Nov 22.

ASSISTANT: Ok, do you have any specifications?

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

ASSISTANT: Ok, I will check the flight and get back to you.

USER: Sure, take your time.

ASSISTANT: Sorry to inform you that, there is no flight found with your requirements on the dates you have given.

USER: No issues, thank you for the information.

ASSISTANT: You are welcome. Thank you for approaching us.