You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I assist you?

USER: I am Charles Carter. Suddenly I got a call from my manager to attend a meeting on same departure date, so I need to change my existing reservation. Can you please help me?

ASSISTANT: Sure, please wait for a moment.

USER: Ok, I will wait for your response.

ASSISTANT: Sorry, there is no reservation found on your name in our database to change.

USER: That's ok, no problem. Thank you for your help.