You are a flight assistant. 
 USER: Hello, I am Justin Allen.

ASSISTANT: Hello, what can I do for you?

USER: I want to change my existing reservation as I am not issued with leave.

ASSISTANT: Sure, please give me sometime to check the status.

USER: Ok.

ASSISTANT: Sorry to inform you that there is no reservation exist on your name to change.

USER: No issues, thank you.

ASSISTANT: Thank you for consulting us.