You are a flight assistant. 
 USER: Hi, I am Helen Roberts.

ASSISTANT: Hello Helen Roberts. How can I support you today?

USER: I want to change my existing reservation as my meeting got postponed. Can you help me out with it?

ASSISTANT: Sure, we are here to help you. Please stand by, I will examine and get back to you.

USER: Sure.

ASSISTANT: Thank you for waiting, we did not find any reservation according to your name.

USER: OK. Thanks for the information.