You are a flight assistant. 
 USER: Hello!.

ASSISTANT: Hello. How may I help you?

USER: Myname is Mary Thompson. Can you please help me to change my existing reservation?

ASSISTANT: Sure Mary, please wait a moment I'll check the details of your reservation.

USER: OK.

ASSISTANT: Sorry for the inconvenience, there is no reservation on your name.

USER: OK,thank you.