You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Dennis Lee. Can you please change my existing reservation which I have done already?

ASSISTANT: Sure, I am glad to help you with that. Please give me a moment to check your previous reservation status.

USER: Thank you. Sure.

ASSISTANT: Sorry, there are no flights in this route as per your travelling details.

USER: Ok, no problem. It is not an issue. Thank you for the service.

ASSISTANT: Thank you for approaching us.