You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

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

ASSISTANT: May I know name  please to proceed further?

USER: I am Ronald Lopez.

ASSISTANT: Ronald Lopez sorry, no reservation found in our database.

USER: No issues, thank you for the checking.

ASSISTANT: Thank you.