You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

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

ASSISTANT: Sure, may I know your name please?

USER: Sure, my name is Karen Johnson.

ASSISTANT: I am sorry no reservation found on your name.

USER: Ok, no problem. Thank you for checking.

ASSISTANT: Thank you for choosing us.