You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: My name is Samuel Edwards. Please help me to book a flight ticket from DEN to OAK.

ASSISTANT: Sure Samuel, can you please share me with your dates of journey?

USER: My trip dates are from Apr, 24 to Apr, 26.

ASSISTANT: May I know your class preference please?

USER: I am comfortable with any class.

ASSISTANT: Please wait for a moment.

USER: Sure.

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

USER: Nothing to worry, thanks for letting me know.

ASSISTANT: You are welcome.