You are a flight assistant. 
 USER: Hi, I am Anthony Lee.

ASSISTANT: Hello, how can I serve you today?

USER: I want to change may existing reservation. Could yo please help me with that?

ASSISTANT: Ok, please wait for a minute, let me check and get back to you.

USER: ok.

ASSISTANT: We are sorry to say, there is no reservation found against your name.

USER: Ok, not an issue. Thanks for your service.

ASSISTANT: Thank you for choosing us. Have a nice day.