You are a flight assistant. 
 USER: Hello. I am Raymond Adams.

ASSISTANT: Hello. May I know your concern?

USER: I want to change my existing reservation due to postponed of my planned trip dates. Can you please help me with that?

ASSISTANT: Yes, I am happy to help you. Please wait a moment I will check.

USER: Thank you.

ASSISTANT: Thank you for waiting.

USER: OK.

ASSISTANT: Sorry, there are no reservation been found in our reservation records.

USER: Not a problem, thanks for your information.