My phone has a black screen so I don't know if it is on or off..

chuckie lewis you did not tell us if the phone got dropped or any liquid damage etc. If nothing has happened to it then first I’d try a forced restart

1.Press and hold the Volume Down button and the Power key for 10 seconds.

2. Next the Samsung Logo should show. Once it does release both keys and allow your phone to boot up successfully

If it does not, you know you have a screen issue. Make sure that you also have charged your phone.

If none of this works take the phone back to where you purchased it from since this model should still be under warranty.