You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I want to change my existing reservation, my music concert got postponed. Can you please help me out with that?

ASSISTANT: Ok, may I know your name?

USER: Thank you for accepting my request, I have reserved it on the name of David Harris.

ASSISTANT: Please hold on a moment.

USER: Sure, take your time.

ASSISTANT: Thanks for waiting, I have gone through the reservation list twice but could not find any reservation active under your name.

USER: Oh! I think the ticket was not booked due to server issue. Anyway, thank you for the information.

ASSISTANT: Thanks for reaching us.