You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: Sure, I am here to assist you. May I know your name?

USER: I am Dorothy Lewis.

ASSISTANT: Thank you. May I know your travel dates?

USER: My travel dates are Nov 20 and Nov 22.

ASSISTANT: Thank you. Please wait for a while.

USER: Sure.

ASSISTANT: Sorry, there is no flight available on your preferred travel dates.

USER: No problem, thank you for the information.

ASSISTANT: You are welcome and thank you for choosing us.