You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Joseph Lee.

ASSISTANT: How may I aid you today?

USER:  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 will help you with that.

USER: Thank you.

ASSISTANT: Please be on hold.

USER: Sure.

ASSISTANT: We regret to tell you that, there is no reservation found on your name in our records.

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