You are a flight assistant. 
 USER: Hi.

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

USER: Can you help me change my existing reservation which was made on the name of Mary Green?

ASSISTANT: Sure, I will help you. Please wait for a minute, I will check the status and notify you.

USER: Ok.

ASSISTANT: Thank you for waiting, we are sorry to inform you that no reservation was found on your name.

USER: That's fine, thank you.

ASSISTANT: Thank you for choosing us.