My experience has been that *many* UA telephone agents do not understand upgrade rules as they apply to gov't fares. I've often had the same experience when I try to upgrade gov't Y fares domestically (they try to charge 15,000 miles rather than 8,000 for a one-way trans-con). Generally, if they give me a hard time I say nevermind, hang up and call back again. Have you already tried this method? I also suspect that the Mileage Plus reps are even less familiar with this issue than reservations agents. Perhaps you can find a friendly reservations agent (someone from the 1K desk, if you're a 1K?) who would help explain the rules to the Mileage Plus folks?