You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be a help for you this evening?

USER: I want to attend my friend's marriage for that I reserved the ticket, but right now I am going by with other friends. So that I want change my reservation, can you help me to change my ticket?

ASSISTANT: Sure, may I know the name on which the ticket is booked?

USER: With Shirley Walker.

ASSISTANT: Sorry, there is no previous reservation found on your name to change.

USER: It's not a problem. Thanks for checking.

ASSISTANT: Most welcome.