My girlfriend and I booked a business/businessfirst/first saver one-way award for 60k miles each from Phuket, Thailand to Denver, CO. The flight has three legs. We are booked in business class for HKT to ICN, business for ICN-SFO, and economy for SFO-DEN because the SFO-DEN leg did not originally have any business award space available (SFO-DEN actually only has economy and first class available). I checked United today and there was an earlier flight for the SFO-DEN leg with 2 available spaces in First/Business First section. We called United and tried to get that changed, but the rep said that the miles are different and we could only book in Economy. Since we booked a business saver award and there are business saver spaces available, aren't we entitled to be able to change our reservation to the premium cabin? We were able to switch our flight, but they were going to charge us to move to economy plus, and couldn't move into business/first seats under our award ticket. The phone rep didn't seem very knowledgeable, so do we just need to call back again until someone know the actual award rules?