Hi lisaann and welcome to Cruise-Chat.
The price drop policy works for bookings made in America. It looks like you may be from the UK, where the policy is different.
Usually, if you call the cruise line or your travel planner, you will be given the lower price. If that didn't work for you, I can only imagine that the same policy is not true for wherever you live.
Perhaps someone else from the UK can advise.