You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation, as my exams got postponed. Can you please help me out with it?

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

USER: Thank you.

ASSISTANT: May I know your name?

USER: Sure, I am Mary Martinez here.

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

USER: Ok, not a problem. Thanks for the information.

ASSISTANT: Welcome, have a nice day.