Many dealers don't want to do that anymore; guess BMW issued some kind of bulletin to that effect to save money
. I'd definitely change it if I were you. But rather than rewarding BMW/dealers with that crap, I'd just change it myself. I did when my car turned 2 years old (but only 8K miles), and used Royal Purple. The tranny fluid made a noticeable difference, especially when cold, and the differential stopped squealing, which was increasingly getting louder. You could also use an independent BMW mechanic. I'd not do it at BMW out of principle, but to each his own. Good luck, and before giving up, I'd call BMWNA and try to push what your maintenance booklet clearly indicates. Take care.