You are a flight assistant. 
 USER: Hello, I am Gregory Mitchell.

ASSISTANT: Hello, how may I help you?

USER: I would like to change an existing reservation due to my interview got post pone. Can you help me in change an existing reservation?

ASSISTANT: Sure, please wait a minute.

USER: Sure.

ASSISTANT: Thank you for your time. There is no reservation found according to your name.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for picking us.