You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: Can you please change my existing reservation, due to my trip with friends has been postponed?

ASSISTANT: Sure, I am glad to help you. May I know your name please?

USER: My name is Donald Hill.

ASSISTANT: Ok, please standby.

USER: Sure.

ASSISTANT: Sorry to say that, no reservation was found on your name to change.

USER: Ok, thanks for your information.

ASSISTANT: Thank you for choosing us.