You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, may I know your name please?

USER: I am Catherine Green.

ASSISTANT: Sorry Green, there is no reservation found as per your name in our database.

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for reaching us.