You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I guide you at this moment?

USER: William Thompson here. I have to do some modification in my previous flight ticket booking that there is a sudden event held at my home town, so I am unable to travel the trip. can you please help me out with changing of my reservation?

ASSISTANT: Sure, I am here to help you. Please wait for a few minutes.

USER: Ok.

ASSISTANT: Thank you for waiting, no reservation was found on your name to change.

USER: That's ok, thank you for your help.

ASSISTANT: Thank you for choosing us.