A 46D is a 46 band with a D cup — a fuller cup. The band does most of the work (around 80% of your support), so if it rides up at the back or the straps dig in, it's the band to fix, not you.
We cut 46D for fuller busts, part of our full 46D–46K range. Not sure 46D is your size? Book a personalized fitting and we'll get it sorted.