You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I want to change existing reservation, please help me out.

ASSISTANT: Ok, may I know your name?

USER: Myself Anna Anderson.

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

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

ASSISTANT: Thank you for reaching us.