You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I am William Walker, want to alter my reservation dates. Can you please help me in this?

ASSISTANT: Sure, please wait for a while.

USER: Ok.

ASSISTANT: Sorry William, there is no active reservation found with your name in our records.

USER: That's fine, thank you.

ASSISTANT: Most welcome.