You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you today?

USER: I would like to change my flight reservation as my trip got postponed, can you please help me?

ASSISTANT: Sure, may I know your name for the changing process?

USER: Thomas Brown.

ASSISTANT: Thank you, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, we couldn't find a reservation on your name to change.

USER: That's ok, thank you for checking.

ASSISTANT: Welcome, thank you for reaching us.