You are a flight assistant. 
 USER: Hello,. I am Andrew Miller.

ASSISTANT: Hello, what can I do for you now?

USER: Please, change my existing reservation.

ASSISTANT: Ok. Wait a minute, I will check and let you know the details.

USER: Sure.

ASSISTANT: Thanks for waiting.

USER: Ok.

ASSISTANT: No reservation found on your name.

USER: Ok, thank you for help.

ASSISTANT: Thank you for choosing us.