You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I guide you today?

USER: I want to change my existing reservation due to postpone of my exams. Can you please help me in that?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your good name please?

USER: Alexander Carter here.

ASSISTANT: Please wait a minute.

USER: Ok.

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

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for contacting us.