I booked 2 tickets on the NWA website and asked for the fully refundable options. The fares came back as "B" fares and the rules stated they were fully refundable. I then called WorldPerks to upgrade them with miles and was told that I needed 10K each way (rather than 5K each way) to upgrade because the fare was fully refundable but not a "full fare". I checked every website box choice I could to make it a full fare.