You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: This is Michael Hernandez. Could you please help me to modify my existing reservation?

ASSISTANT: Please give me a moment. I can get back to you.

USER: OK.

ASSISTANT: Thanks for your waiting.Sorry to say that Michael, unfortunately there is no reservation found under your name.

USER: OK, thank you for your information.

ASSISTANT: Welcome, have a nice day.