You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I help you today?

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

ASSISTANT: Sure, may I know your good name please?

USER: Sure, Margaret Miller here.

ASSISTANT: Please wait a minute.

USER: Sure.

ASSISTANT: Sorry, there is no reservation found on your name to change.

USER: No issues, thank you for the information.

ASSISTANT: Thank you for choosing us.