OK don't panic.
First you should know there's plenty of S4 clones out there (HDC Galaxy S4, HDC Spark, Meso S4, unidentified Dual SIM S4 clone, etc., etc.).
Second you have to be 100% sure your system is properly set up.
If you or a friend of you has another MTK (better if MTK6589) smartphone check if everything works properly (drivers, flashing, etc.).
If not install everything properly and in a clean Windows partition without 300 USB drivers and devices.
Once you are done with what written above come back and we will see.
In the meantime upload a pic of the backside without cover and battery, but please be sure to hide the printed IMEI number.
Sent from my Samsung Galaxy Note with Tapatalk 2