Unlike Samsung’s Android devices (which use Odin), the GT-C3520 requires because it uses a Broadcom or Infineon baseband processor. The two most reliable tools are:
This is the operating system for the Samsung GT-C3520. It contains the core system files necessary for the phone to function.
Using firmware meant for a different model (e.g., GT-C3520i vs GT-C3520) can permanently damage the device.