You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you for today?

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

ASSISTANT: I will help you with that.

USER: Thank you.

ASSISTANT: May I know your name?

USER: My name is Joseph Green.

ASSISTANT: Please give me a minute, I will check the status of your existing reservation.

USER: Ok.

ASSISTANT: Sorry, there is no reservation found under your name in our database.

USER: Not an issue, thank you for the information.

ASSISTANT: Thank you for contacting us, have a nice day.