You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. What can I do for you today?

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, could I know your name please?

USER: I am David Halls.

ASSISTANT: Please hold on, let me check. Sorry Halls, I have not found any reservation by your name.

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

ASSISTANT: Thank you for contacting us.