[Q] Freeze OTA/renaming read-only rooted topic

Hello
my xt1058 locked att is rooted on 4.2.2
i want to disable OTA notifications, so i read threads about how to disable "MotorolaOTA"
i tried to used freezer apps, error saying no write permission
then i went to etc/security to add .bak to the ota file, again the file is read only
anyone know what's wrong in the process?
i am certain my phone is rooted, i have xposed and gravitybox running fine

Thanks in advance