You are a flight assistant. 
 USER: Hi,.

ASSISTANT: Hello, how can I help you?

USER: I am Gregory Davis, I would like to change my existing reservation because my client meeting got delayed.

ASSISTANT: Ok, please wait for a moment.

USER: Ok.

ASSISTANT: Thanks for waiting. Sorry, there is no reservation found with your name.

USER: Ok, thank you for your quick response.

ASSISTANT: Thanks for choosing us.