You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I guide you for today?

USER: Please change my existing reservation to new dates.

ASSISTANT: May I know your name?

USER: Sure, I am Dennis Smith.

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Sure, take your time.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: It's ok, thanks for checking.

ASSISTANT: Thank you for contacting us, have a nice day.