You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I need to change my existing reservation, can you please help me?

ASSISTANT: Sure, I am here to help you for this. Let me check your reservation status in our database.

USER: Thank you for kind response.

ASSISTANT: For changing the reservation, may I know your name please?

USER: Myself Dennis Lee.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Sorry to intimate, no reservation is found with your criteria.

USER: That's ok, thank you for searching my details.

ASSISTANT: Thank you very much for contacting our agency.