You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I serve you today?

USER: I made a reservation earlier to meet my project manager. Appointment has been postponed due to some issues. Can you please change my existing reservation?

ASSISTANT: Sure, may I know your name for changing?

USER: I am John Hernandez.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry, no reservation found done previously on your name.

USER: It's not a problem. Thanks for your information.

ASSISTANT: Thank you for picking us.