You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I be a help for you?

USER: I have made a mistake while booking the ticket. I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, I will help you. May I know your good name please?

USER: My name is Gary Parker.

ASSISTANT: Sorry, there is no reservation found on your name in our data base to change.

USER: Ok, I think I didn't book the ticket. Anyways, thank you for the information.

ASSISTANT: You are most welcome.