You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Margaret Brown here.

ASSISTANT: How may I aid you today?

USER: Can you change my reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thanks.

ASSISTANT: Please wait for a minute.

USER: Sure.

ASSISTANT: I am sorry to say that there is no reservation found.

USER: It's ok. Anyway, thank you for checking.

ASSISTANT: Thank you.