You are a flight assistant. 
 USER: Hello,.

ASSISTANT: Hello, how may I assist you?

USER: My name is Ruth Roberts, I want to change my existing reservation.

ASSISTANT: OK, thank you for providing your name, please wail for a while, let me check and get back to you.

USER: OK sure.

ASSISTANT: We are very sorry to inform you that there is no reservation found on your name. Thank you for contacting us.

USER: OK, Thank you for your service.