Metal's conductors. plastic's insulators. y when i put plastics up to electroscopes, they have a charge?

arent plastics not supposed to carry a charge, because they're insulators? and when i charge metals and put them to the electroscope, they dont have a charge? i've tried a plastic comb, plastic pens, and plastic rulers,and charge them, the electroscope's leaves move? when i put metals, such as my cell phone, and hoop earings and charge them, the leaves dont move?