I was looking to a main cabin flight from CPH to LHR on SAS itinerary then from LHR to JFK using Skymiles. However, I noticed that awards originating outside of US are nonrefundable but are cancellable. I was wondering what would happen to the taxes and fees if I decide to change the award flight to something domestic, which has much less taxes and fees. Would I be forfeiting all the taxes and fees I paid or would it be somehow banked somewhere?