You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I aid you today?

USER: Please help me in changing of my existing reservation.

ASSISTANT: Sure, I am glad to help you to change it.

USER: Thank you.

ASSISTANT: Can I have your name please?

USER: Jacob Robinson.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Sorry to tell you that, there was no reservation found on your name to change it.

USER: Ok, no problem. Thank you.

ASSISTANT: Thank you for availing us.