You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I give assistance to you?

USER: Can you help me to change my existing reservation which is on the  name of Margaret Green?

ASSISTANT: Sure, I am glad to help you.

USER: Thanks.

ASSISTANT: Please wait for a few minutes.

USER: Sure.

ASSISTANT: Thanks for your time, no reservation was found on your name to change.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for approaching us.