You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you?

USER: I would like to change my existing reservation, please help me out.

ASSISTANT: Ok, may I know your name please to proceed further?

USER: My name is Helen Wilson.

ASSISTANT: Helen, there is no reservation found with your details.

USER: It's ok, thank you for your information.

ASSISTANT: Thank you for choosing us, have a good day.