A520F unlock U4 BB supprted or not

This operation takes 5 credits.Continue? Yes
[ 4/14/2018 5:36:00 PM ] Searching Samsung modem... detected COM370
[ 4/14/2018 5:36:00 PM ] Reading phone info...
[ 4/14/2018 5:36:00 PM ] Model: SM-A520F
[ 4/14/2018 5:36:00 PM ] AP version: A520FXXS4BRA1
[ 4/14/2018 5:36:00 PM ] CSC version: A520FOJV4BRA2
[ 4/14/2018 5:36:00 PM ] CP version: A520FXXU4BRAB
[ 4/14/2018 5:36:00 PM ] Product code: XSG
[ 4/14/2018 5:36:00 PM ] Phone SN: R58K34YFVJE
[ 4/14/2018 5:36:00 PM ] IMEI: 356650095484988
[ 4/14/2018 5:36:00 PM ] Unique number: CBJ00CA24ECF325
[ 4/14/2018 5:36:00 PM ] Searching Samsung diag port... detected COM297
[ 4/14/2018 5:36:00 PM ] Reading phone info... OK
[ 4/14/2018 5:36:00 PM ] CP version: A520FXXU4BRAB
[ 4/14/2018 5:36:00 PM ] CP build: Jan 19 2018 19:59:12
[ 4/14/2018 5:36:00 PM ] Reading data from phone... error (1)
[ 4/14/2018 5:36:00 PM ] Searching server... OK
[ 4/14/2018 5:36:00 PM ] Checking available files... not found compatible file
[ 4/14/2018 5:36:00 PM ] Try downgrade modem if possible


And i try downgrade modem then go unknown but i restore it again
any way to unlock it @ U4


thanks