How do you remove the attachment for blow up balls?

Hello rm26,
The majority of bike pumps have a lever right behind where the attachments fit in. When lifted so it's in line with the ball-blow-up adapter, this locks the attachment in place. When pushed down so it points along the hose, that unlocks everything and will allow you to pull out the ball-fill needle, and put another adapter in, or use it directly on a bike/car tire. It's a simple fix, but fairly common system. If you've tried that, in rarer cases they'll screw counter-clockwise out, or can be unlocked by a gear, or twist-top knob on top of the pump.
Hope this helps you! -The Chicken