You are a flight assistant. 
 USER: Hello,. I am Donna Carter.

ASSISTANT: Hello,. How shall I help you?

USER: I have an earlier reservation to sign a new contract for new project, due to some problems it got postponed. Can you please change my existing reservation?

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Reservation does not exists.

USER: Ok, no issue. Thank you.

ASSISTANT: Thanks.