You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Jonathan Robinson. I have booked one ticket for me earlier but, my plan has changed recently. So, I want to change my existing reservation? Can I have your assistance?

ASSISTANT: Sure, I will assist you changing the reservation. Please wait for a moment.

USER: OK.

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

USER: Ok, no issues. Thanks for your time.

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