You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I aid you today?

USER: I would like to change my existing reservation because my trip dates are got postponed, can you help me?

ASSISTANT: Sure, I am here to help you. could you please help me with your name?

USER: I am Steven Hill.

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

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

ASSISTANT: Thank you for opting us.