Losing Space

[kentaddition]

I only used 12.5 gb and my 16gb s9 says its full, does anyone have a solution to this problem?

[Acreo Aeneas]

Have you tried the reset button on the back? (hold it down for 3+ seconds before releasing)

If that doesn't help, you can try reloading the firmware again. And if that doesn't help, reformat and then reload the latest firmware.