1- Open ATF Box setup.
2- Select Phone type as BB5.
3- Select Model no. C2-01: RM-721.
4- Under "Write Flash", select Phoenix INI & USB mode.
5- Tick Mark Factory reset and click on flash.
6- Switch off the mobile & press power key while connecting to USB.
7- Flashing starts.
8- When flashing ends, reboot your mobile.