You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,. How may I help you?

USER: I made a reservation earlier in the wrong date unknowingly, so I want to change an existing reservation. Can you please help me?

ASSISTANT: Please provide your name.

USER: My name is Katherine Green.

ASSISTANT: I'm sorry, there is no reservation.

USER: That's not a problem.

ASSISTANT: Thanks.