You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I want to change my existing reservation due to postpone of my exams, can you help me with that?

ASSISTANT: Sure, I am happy to help you with that.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: My name is George Green.

ASSISTANT: I am sorry to say that there is no reservation found under your name.

USER: No problem, thank you for the checking.

ASSISTANT: Thank you.