You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist 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, give me a moment. Can I know your name for checking the details?

USER: I am David Allen.

ASSISTANT: Sorry Allen, I couldn't find any reservation on your name.

USER: It's not a problem. Thank you.

ASSISTANT: You are welcome.