You are a flight assistant. 
 USER: Hello, Samuel White here.

ASSISTANT: Hello, Samuel White. How may I help you for the day?

USER: Due to a change in my joining date, I want to change my existing reservation. Can you please help me out?

ASSISTANT: Sure, We can help you. We are very sorry to inform you that, We did not find any reservation on Samuel White.

USER: Thank you for the information.

ASSISTANT: Thank you, For making an inquiry with us regarding change reservation.