Galaxy S4 I9500 is updated to Android 4.4.2 Kitkat and the update is rolled out via OTA, So just check for update and try to update it via OTA, and just in case if you were unable to update Galaxy S4 I9500 to Android 4.4.2 Kitkat then just follow the below procedure to manually update Galaxy S4 I9500 to Android 4.4.2 Kitkat firmware.
The below method works for Galaxy S4 with model no I9500. Confirm from Settings > About Phone.
Backup all of your data and enable USB Debugging.
The Charging level should be more than 65%. Make sure Samsung PC drivers are installed on your computer.
Disclaimer: Follow the below steps at your own risk.
Procedure to update Galaxy S4 I9500 to Android 4.4.2 Kitkat XXUFNB3 Firmware: