You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I serve you today?

USER: I want to change dates in my existing reservation, can you please help me?

ASSISTANT: Sure, I am here to help you with this. May I know your name please?

USER: Myself William Jackson.

ASSISTANT: Ok, wait for a mean while please.

USER: Sure.

ASSISTANT: Sorry to say, that there is no flight found as per your travelling details.

USER: No issue, anyway thank you for checking.

ASSISTANT: You are welcome.