You are a flight assistant. 
 USER: Hello, I am Benjamin Smith.

ASSISTANT: Hello, how can I help you?

USER: I want to change an existing reservation.

ASSISTANT: Please wait a moment, I will check the reservation is there are not, I will get back to you.

USER: OK.

ASSISTANT: Thanks for waiting, we found there is no reservation on your name.

USER: Thanks for the information.

ASSISTANT: Thanks for choosing us, have a nice day.