You are a flight assistant. 
 USER: Hello. I am Kevin Phillips.

ASSISTANT: Hello, how can I help you?

USER: Can you please book a flight ticket from LAS to DTW?

ASSISTANT: May I know your desired travel dates please?

USER: Sure, I need to travel on dates of 08/18 and 08/20.

ASSISTANT: Please wait a while.

USER: Sure, take your time.

ASSISTANT: Sorry to say, there is no flight on your desired travel dates.

USER: Oh! It is sad to hear. Anyway, thank you for your time.

ASSISTANT: Thank you for opting us. Have a nice day.