You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, Good morning. May I know your name please?

USER: I am Brian Johnson.

ASSISTANT: Brian, how can I help you?

USER: I just want to change my existing reservation to next week. Can you help me out?

ASSISTANT: Sure, I am happy to help you.

USER: Sure.

ASSISTANT: Please wait for a while, I will check the existing reservation details.

USER: Ok.

ASSISTANT: Sorry Brain, there is no reservation found on your name.

USER: That's fine. Thank you for your help.

ASSISTANT: Do you have any other preferable dates to travel?

USER: No.

ASSISTANT: Ok.

USER: Thank you.

ASSISTANT: You are welcome.