I have a similar problem where I keep getting a notification that Talkback is active when the app is showing up in App Manager as disabled. Talkback isn't working, just the notification.
I've read other similar threads that absolutely mystify me with talk of double finger swipes, holding down buttons and similar proposals about which I know nothing, but still no result. Phone is a Samsung Galaxy S4 running Android 5.0.1.
If all else fails I think I'll just go back to Apple; it generally just worked.