You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I assist you today?

USER: Please change my existing reservation.

ASSISTANT: Ok, may I know your name to check reservation?

USER: I am William Lopez.

ASSISTANT: Please, hold on for a while.

USER: Sure.

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

USER: Thanks for the assistance.

ASSISTANT: Thank you for availing us.