I am in manual mode (M on the top left scroll wheel above the on button) using a sigma 10-20mm F4-5.6 and then I spin the scroll wheel (which has a "set" button in the middle) below the 'q' button, the aperture doesn't change.
It also won't change in Aperture priority mode (AV Mode)
I am a noob with cameras, so I am really stumped