You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Michael Johnson.

ASSISTANT: How can I guide you now?

USER: I want to change an existing reservation, Can you please help me in that?

ASSISTANT: Ok, please allow me to check with your previous booking for a moment.

USER: Sure.

ASSISTANT: Sorry to inform you Michael Johnson, there is no reservation found by your name.

USER: That's ok, not a problem. Thanks for your information.

ASSISTANT: Thank you for choosing us. Have a nice day.