You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Amy Anderson.

ASSISTANT: OK Amy, how can I assist you for today?

USER: I have already reserved my ticket, but I want change an existing reservation . Could you please help me with this?

ASSISTANT: Sure, please wait for a moment.

USER: Sure.

ASSISTANT: Sorry Amy, there is no reservation found on your name.

USER: OK. Thank you for your wonderful service.

ASSISTANT: Thank you for approaching us.