You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I want to change my existing reservation. Can you help me for this one?

ASSISTANT: Sure, I am here to assist you. May I know your name please?

USER: Sure, Ryan Miller here.

ASSISTANT: I am really sorry to tell  you, there is no active reservation found with your name to change the details.

USER:  No issues, thank you for the information.

ASSISTANT: My pleasure to inform you, thank you for opting us.