No double billing from Norwegian but also no Customer Service when there may be a problem!
My advice is to forget Norwegian if you are looking for a quality cruise line!
I have been trying to get through to get some action with their "Customer Relations" department for over six months now!
They have, in that time, gone through THREE directors. And I still have no direct response.
All this after they dumped my luggage in a pool of water on dock.
Stay away from them.