You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I'm John Clark.

ASSISTANT: How may I aid you today?

USER: My scheduled examination dates has been postponed. So, I would like to change my existing reservation. Can you please help me with that?

ASSISTANT: Sure, I am glad to help you with that. Please wait a moment to check your previous reservation.

USER: Sure, take your time.

ASSISTANT: Sorry to inform you that, there is no reservation found with your name in our records.

USER: Ok, no issues. Thank you for checking.

ASSISTANT: Thank you for reaching us, have a great day.

USER: You are welcome.