You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you?

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, I can help you with that. Can you please provide your name?

USER: I am Andrew Johnson.

ASSISTANT: Sorry Andrew, there is no reservation found.

USER: It's ok. Thanks for your helping.

ASSISTANT: Thank you, have a nice day.