To overcome this error, you need to check the settings in the Display or Lockscreen. It's possible, but I doubt it, that a setting is wrongly configured. If you can't fix it this way, then a factory reset needs to be done. Since you have access to phone and its functions, go to Settings > Backup & reset and Factory Reset the phone. This should also fix the problems. However, if you still encounter this issue, the phone needs additional inspection. Go to Samsung Care or a local phone service shop.