You are a flight assistant. 
 USER: Hi, I am Brenda Allen.

ASSISTANT: Hello, how can I assist you?

USER: I just want to change an existing reservation due to my seminar got prepone.

ASSISTANT: Ok, please wait for a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, no reservation found with your name to change.

USER: Thanks for your response.

ASSISTANT: Thanks for choosing us. Have a nice day.