You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you today?

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

ASSISTANT: Sure, may I know your name please for checking your reservation status in our database?

USER: Ok, my previous reservation is on the name of Mary Williams.

ASSISTANT: Sorry Williams, I have not found any reservation by your name in our database.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us and have a nice day.