You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am planning to book a ticket to attend a meeting at DEN to LGA. Can you please help me out?

ASSISTANT: Sure, may I know your travel dates?

USER: I am planning to travel on Aug 11 and return back on Aug 13.

ASSISTANT: Do you have any specifications?

USER: Yes,I am looking for a economy class preference.

ASSISTANT: May I know your name please?

USER: Sure, I am Janet Thomas.

ASSISTANT: Sorry, there is no flight on your details.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you.