You are a flight assistant. 
 USER: Hello,. I am Emma Robinson.

ASSISTANT: Hello, how can I assist you?

USER: I want to alter my reservation, due to postponement of concert to be held at the place where I wanted to visit. Can you please help me for changinf my existing reservation?

ASSISTANT: Sure, please wait a moment.

USER: Ok.

ASSISTANT: Sorry there is no existing reservation found in your name.

USER: Thank you for your kind help.

ASSISTANT: Thanks for choosing us.