You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: Can you please help me to change my existing reservation?

ASSISTANT: Sure, may I know your name for the changing process?

USER: Sure, my name is Mark Campbell.

ASSISTANT: Thank you, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry, we couldn't find a reservation on your name to change.

USER: Ok, thank you.

ASSISTANT: Welcome, thank you for reaching us.