You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: I am Donna Carter. I want to change my existing reservation due to postpone of my exams, so can you help me with this?

ASSISTANT: Wait a moment.

USER: Sure.

ASSISTANT: There is no reservation found on your name to change it.

USER: No problem, thank you for the information.

ASSISTANT: Thanks for reaching us, have a nice day.