You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I address you today?

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

ASSISTANT: Sure, can I know your name please?

USER: Cynthia Taylor here.

ASSISTANT: Please give me a moment.

USER: Sure.

ASSISTANT: We are sorry to inform you that there is no reservation found with your given name,.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.