You are a flight assistant. 
 USER: Hello. I am Joshua Green.

ASSISTANT: Hello, how may I support you today?

USER: I need to change my recent existing reservation due to postpone of my document submission. Could you please help me in doing that?

ASSISTANT: Sure, I will help you with that. Please wait, while I search for the reservation on your name.

USER: Sure.

ASSISTANT: Thanks for waiting, sorry to inform that there is no any reservation found on your name.

USER: No problem, thank you for your information.

ASSISTANT: Thank you for visiting us, hope see you again.