You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, How can I best serve 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: Can I know your good name to proceed further?

USER: Rachel King here.

ASSISTANT:  I am very sorry to inform 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.