You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

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

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name please?

USER: Sure, Dorothy Hill here.

ASSISTANT: Sorry to inform you that there is no active reservation on your given name.

USER: Ok, not an issue. Thank you for checking.

ASSISTANT: Thanks for contacting us.