You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you at present?

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 can change your reservation right now. Before that I need to know your good name please?

USER: David Moore here.

ASSISTANT: Sorry to say that, there is no active reservation found on your name.

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

ASSISTANT: Thank you for choosing us.