Download program Phoenix Service Softwar and Diegor.

If you have installed the PC Suite, you need to remove it completely, it is advisable to clean the registry of the relevant records. Install Phoenix Service Softwar and Diegor.
Download the firmware and unzip it.

Start Phoenix Service Software. In the File menu, select Manage Connections. In the opened window click the Add button. Add a new user, specifying the USB in connection settings.
Connect your phone to the computer it should be detected and should start installing its drivers.
In the File menu, select Scan Product, appear the icon of the connected cable.

Go to the tab Flashing/Firmfare Update. If the phone has the firmware, the Product Code will indicate its version. To change it, click on the icon and select the desired version. Press Start. Will start the firmware update during which the phone switches to Test Mode, and then restarts with the updated firmware version.