You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, How may I help you today?

USER: Due to bad weather, I want to change my reservation.

ASSISTANT: Ok.

USER: Can you help me?

ASSISTANT: Sure, I will help you. May I have your good name please?

USER: I am Joseph Johnson.

ASSISTANT: Ok. Thanks for waiting, but we are sorry to inform you that no reservation is existed.

USER: No issue, Thanks for the information.

ASSISTANT: Ok, Thank you.