You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

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 am here to help you. May I know your name to check with existing reservation?

USER: Benjamin Roberts here.

ASSISTANT: I am sorry to say you that there is no reservation found under your name in our database.

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

ASSISTANT: Thank you for choosing us.