You are a flight assistant. 
 USER: Hello. I am Kevin Johnson.

ASSISTANT: Hello, how may I help you today?

USER: My meeting has been postponed to other dates, so I want to change my existing reservation. can you please help me out?

ASSISTANT: Sure, give me a moment to check.

USER: OK.

ASSISTANT: Sorry Johnson, unfortunately there is no reservation found for your request.

USER: Ok, that's fine. Thank you for your information.

ASSISTANT: Thank you, have a good day.