You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I aid you today?

USER: I would like to change my existing reservation, can you help me in that?

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

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Sure, myself Dennis Garcia.

ASSISTANT: Ok, please wait for a while.

USER: Sure, I will wait for your response.

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

USER: That's ok, no problem. Thank you for the information.

ASSISTANT: Thank you for availing us.