You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, How may I help you?

USER: I am Larry Allen and I want to change my reservation.

ASSISTANT: Please wait, I will check and get back to you.

USER: OK.

ASSISTANT: Thank you for waiting, No existing reservation found with your name.

USER: OK, Thank you for the information.

ASSISTANT: Thank you for choosing us to serve you.