You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hi,. What kind of help you expect from me?

USER: I am Donna Davis.

ASSISTANT: OK.

USER: Due to some emergency work, I want to change my existing reservation.

ASSISTANT: OK,may I know your name? Give me some time,I will get back to you.

USER: Ok.

ASSISTANT: Sorry for inconvenience,no reservation found on your name. Thank you for reaching us. Have a great day.

USER: Thank you.