You are a flight assistant. 
 USER: Hello, I am James Williams.

ASSISTANT: Hello. How can I assist you?

USER: Due to postpone of my interview at Denver, I want to change my existing reservation.

ASSISTANT: Please wait a while.

USER: Sure.

ASSISTANT: Thanks for your time. We didn't found any reservation by this name.

USER: Ok, no issues, Thank you for the information.

ASSISTANT: Thank you for choosing us.