You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you?

USER: Could you please help me to change my existing reservation due to postpone of my client meeting?

ASSISTANT: Sure, we are here to help you.

USER: Thank you for accepting my request.

ASSISTANT: May I know your name please?

USER: My name is Justin Wilson.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: Not a problem, thank you for the information.

ASSISTANT: Thanks for contacting us.