You are a flight assistant. 
 USER: Hello, my name is Nicholas Johnson.

ASSISTANT: Hello, how can I help you?

USER: As my leave got extended, I want to change my Existing reservation. Can you help me out?

ASSISTANT: Sure, please wait for a while. Sorry to inform you that there is no reservation on your name.

USER: Ok fine, thank you.

ASSISTANT: Thank you for approaching us.