You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, may I know your good name please?

USER: William Parker.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name in our database to change.

USER: No problem, thank you.

ASSISTANT: Thank you for reaching us.