You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Can I know your name?

USER: Benjamin Martinez here.

ASSISTANT: Sorry, there is no reservation by your name.

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

ASSISTANT: Thank you.