Apparently people are unable to understand clearly written descriptions. Asking pointless irrelevant questions only suggests a propensity to cheer lead for the cruise line. Understand, the issue HAS NOTHING TO DO WITH THE INSURANCE POLICIES IN PLACE. The issue is that NCL / Oceania is unwilling or unable to produce proof of paying a charge for which it billed the passenger.
OP, I wish I could offer some useful suggestion. I can't, but it does seem that you are quickly approaching a point at which legal guidance may be necessary.