You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

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

ASSISTANT: Sure, may I know your good name?

USER: Myself William Lopez.

ASSISTANT: Please stand by.

USER: Ok.

ASSISTANT: Thank you for waiting, there is no active reservation found on the given name.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you.