[Q] Samsung Galaxy Tab 4 8.0 Error System Has been modified in an unauthorized way topic

So I rooted my device with Towelroot. I checked that it was rooted and I used my device for sometime and then I thought I really didnt need root so I unrooted my device through superuser. I used an app called root checker and it said that my device didnt have root permissions. So now I need OTA updates and it says that my device had been modified in an authorized way? Did I unroot it properly or is there another way to fix this or unroot my device. I am looking forward to your replies.
Thanks!