How can I permanently delete contacts? I delete and they keep coming back even after backup or stopping syncing.
I feel like there is some sort of backup/sync going on that you're not aware of...
one option is to submit an issue report when it happens again (best to recreate the issue if you can) through Samsung Members app. The phone is only have to hold about 30min worth of activity log, so if you wait too long after the issue occurs the techs won't be able to see what happened that caused the problem.
Hope this helps.