a lot of people having this problem after trying a lot of methods and installing ROMS, KERNELS, and all other default RUUS the problem has been solved by me 
steps :
1.S-Off
2.if ur bootloader is unlocked re lock it
3.install the default RUU for ur device region
4.unlock ur bootloader again
5.install a recovery
6.root ur device
7.make backup for ur phone
8.disable ur fastboot from power in settings
9.install geenify full version with donation
10.enable cut wake up and system greenify
11.greenify an app called Download manger and do it also for settings
12.power off ur device remove the battery for 5 min then power on
13.use ur device randomly and lock ur screen when some one calls reject and when it still ringing hurry and unlock ur screen go to greenify and cut smartSyncDataLinkTurnOffReceiver from download manger
14.go to setting apps all and search for download manger and disable it
:good::good::good::good::good::good::good::good::good::good::good::good:
thats it ur mobile is now great and ready for use when the screen is locked
thanks for reading
steps :
1.S-Off
2.if ur bootloader is unlocked re lock it
3.install the default RUU for ur device region
4.unlock ur bootloader again
5.install a recovery
6.root ur device
7.make backup for ur phone
8.disable ur fastboot from power in settings
9.install geenify full version with donation
10.enable cut wake up and system greenify
11.greenify an app called Download manger and do it also for settings
12.power off ur device remove the battery for 5 min then power on
13.use ur device randomly and lock ur screen when some one calls reject and when it still ringing hurry and unlock ur screen go to greenify and cut smartSyncDataLinkTurnOffReceiver from download manger
14.go to setting apps all and search for download manger and disable it
:good::good::good::good::good::good::good::good::good::good::good::good:
thats it ur mobile is now great and ready for use when the screen is locked
thanks for reading