You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Jonathan Lee.

ASSISTANT: How may I assist you now?

USER: Due to postpone of my seminar, I would like to change my existing reservation. Can you please help me in changing?

ASSISTANT: Sure, please allow me to check with your previous reservation.

USER: Ok.

ASSISTANT: Sorry to inform you, there is no single reservation available by your name.

USER: Ok, no worries at all. Thank you.

ASSISTANT: Have a great day ahead.