You can increase your number (going from 34 to 36, lets's say) by adding muscle to your chest and back. Cup size (going from A to C), unfortunately is another matter and mostly dependent on high enough bodyfat, implants or something to fill the cup. Contrary to popular belief, working your back and chest will not make your breasts look smaller. I think it's greatly improved mine. Also, the added back width and chest muscle size make the waist look smaller.