You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Amy Green.

ASSISTANT: Oh.

USER: I want to change my existing reservation.

ASSISTANT: OK. Give me a moment to check your existing reservation?

USER: OK.

ASSISTANT: Thank you for being so patient. Sorry for trouble, No reservation has found on your user.

USER: Thank you.

ASSISTANT: Have a nice day.