You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you for the day?

USER: I just want to change my existing reservation, due to my trip with my friends has been postponed. Can you please help me to make some modifications?

ASSISTANT: Sure, may I know your name?

USER: Sure, my name is Nancy Roberts.

ASSISTANT: Sorry, there is no reservation found on your name to change.

USER: Ok, thanks for your information.

ASSISTANT: Thank you for contacting us.