You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: I want to change my existing reservation, because of postpone of my exam. Can you please help me?

ASSISTANT: Sure, I will help you, can I know your good name?

USER: Sure, myself Margaret Lopez here.

ASSISTANT: Sorry, there is no reservation found on your name.

USER: That's fine. Thank you for your information.

ASSISTANT: Thank you for reaching us.