You can try Reset All Settings if you have not. Go to Settings-->>General-->>Reset and then choose Reset All Settings.
If you choose "Reset All Settings", some of your iPhone settings will be reset to factory default settings instead of a complete removal of settings. After that, your iPhone will reboot. "Reset All Settings" will erase your preferences for Sound, General, Bluetooth, Brightness & Wallpaper, WLAN network, Notifications, Privacy and so on. When you get ready to reset all your iPhone settings, Apple will send you warning messages for twice to make sure whether you really mean to erase the previous preference settings or not.
Axel F.