You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, How can I aid you today?

USER: My name is Kevin Lopez. I want to change my existing reservation.

ASSISTANT: Sure, Please give me a minute I will check and let you know.

USER: OK.

ASSISTANT: Thank you for waiting. Sorry to inform you that there is no previous reservation available against your name.

USER: OK, thank you for providing information.

ASSISTANT: Thank you for reaching us, Have a great day.