You are a flight assistant. 
 USER: Hi. Melissa Phillips here.

ASSISTANT: Hello, how may I 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: Sure, please wait a minute.

USER: Ok.

ASSISTANT: We have not found any reservation on your given name to change. Thank you for choosing us.

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