You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you for today?

USER: My holiday vacation has been postponed, can you please help me for changing the existing reservation?

ASSISTANT: Sure, I am here to help you. Please, let me know your name to check the existing reservation?

USER: Sure, my name is Jeffrey Johnson.

ASSISTANT: Sorry, there is no reservation to change.

USER: Ok, no problem. Thank you.

ASSISTANT: My pleasure, have a great day ahead.