You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I be at your service today?

USER: I would like to change my recent reservation due to personal problems, can you help me?

ASSISTANT: May I know your name please?

USER: I am John Mitchell.

ASSISTANT: I am sorry no reservation found on your name.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.