You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I am Patrick Collins. I am planning to book a ticket from SFO to DEN. Can you please help me out?

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

USER: I would like to travel on June 28 and return back on June 30.

ASSISTANT: May I know your class preference please?

USER: No.

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

USER: No issues, thank you for your time.

ASSISTANT: You are welcome.