You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

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

ASSISTANT: Sure, may I know your name please to check the status of your reservation?

USER: My name is Anna Johnson.

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

USER: Ok, no problem. Thank you for your information.

ASSISTANT: Thank you for choosing us.