So I have a stock unrooted Note 3 rocking regular touchwiz and when I get a text it'll come once but then again a few seconds later, both times with the notification. Does this in the regular messages app and in hangouts if I enable SMS.
I've uninstalled all my other messaging apps in case that was the problem but that didn't fix it.
It happens with everyone so I know it's a problem with my phone.
Tmobile customer service is awful and couldn't help beyond offering to replace the phone if I pay shipping and go phoneless for a week.