The first thing you need to check is the Device Administrators section. Go to Settings > Security > Device Administrators. Disable any application from that location and delete it from the list. Long tap on the apps and select Delete. If you still experience weird behavior, go to Settings > Backup and Restore. Before that copy all the items(music, texts, images, etc) to the PC. Choose Factory Reset from Backup and Reset and the phone will be wiped. Reconfigure the phone back, restore the content with Kies and that's it.