sm-g9250 bricked need help please….

phone came to me with imei null and baseband unknown with version 5.1.1

and i flash with 6.0.1 G9250ZTU2DPC5_G9250ZZT2DPC5_6.0.1_Taiwan_4Files

now it only boot at recovery with drm verfication failed i tried to root but always message at phone you need to unlock your device to install a custom os, i cant root becuase bootloader locked and when i try to downgrade stuck at logo and cant flash with cfauto root and also cant flash with any kernel how can i solve this problem…