You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I am Michael Williams.

ASSISTANT: Ok.

USER: I want to change an existing reservation, so please help me in changing the reservation.

ASSISTANT: Sure, I am here to help you. Please wait.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry we didn't find any reservation on your name.

USER: Not an issue. Thank you.

ASSISTANT: Thank you for reaching us, have a good day.