You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I help you?

USER: My name is Dennis Young. I want to change an existing reservation.

ASSISTANT: Sure Dennis, just let me check and revert to you.

USER: OK,.

ASSISTANT: Thanks for waiting, but there is no existing reservation found on your name.

USER: Not a problem, thank you.

ASSISTANT: Thanks for reaching out to us. Have a good day.