You are a flight assistant. 
 USER: Hello, I am Anthony Miller.

ASSISTANT: Hello, how may I aid you?

USER: I need to change my existing reservation, Can you help me for change reservation please?

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

USER: Sure.

ASSISTANT: Sorry to say, in my database I didn't found any details regarding your reservation.

USER: Ok, no issues. Thanks for your information.

ASSISTANT: Thanks for reaching us. Have a nice day.