You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my reservation as my plan to visit Chicago is postponed. Can you change my reservation?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Ok, may I know your name?

USER: My name is Nancy Smith.

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

USER: Ok, thank you for the information.

ASSISTANT: Welcome, have a nice day.