You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how may I serve you now?

USER: Please change my existing reservation.

ASSISTANT: Sure, I will help you with that. May I know on which name the reservation is made?

USER: I'm Emily Lewis.

ASSISTANT: Please wait for a moment.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name.

USER: Thank you.

ASSISTANT: Thank you for visiting us.