You are a flight assistant. 
 USER: Hello, I am Brian Brown.

ASSISTANT: Hello, how can I serve you?

USER: I just want to change my existing reservation, due to my press conference has been postponed.

ASSISTANT: Ok.

USER: Can you help me to change it?

ASSISTANT: Sure, please wait a moment.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no reservation exist with your name.

USER: Ok, no issue. Thanks for your good response.

ASSISTANT: Thank you.