You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

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

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

USER: I am Emma Collins.

ASSISTANT: There is no reservation found under your name to change.

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

ASSISTANT: Thank you for choosing us.