You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Alexander Green.

ASSISTANT: How may I assist you?

USER: I want to change my existing reservation, please help me out.

ASSISTANT: Sure, I am here to help you out.

USER: Thank you.

ASSISTANT: Wait a moment please.

USER: Ok.

ASSISTANT:  Alexander Green, we regret to inform you that there is no reservation found on your name in our records.

USER: No issues thanks for the information.

ASSISTANT: Thank you for reaching us.