You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: I want to change my existing reservation due to postpone of my client meeting. Can you help me in changing?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Please provide me your name.

USER: My name is Stephen Anderson.

ASSISTANT: Sorry, no reservation found on your name to change your reservation.

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

ASSISTANT: Welcome, have a nice day.