1- Download Sony Xperia Flash tool & Unlock file.
2- Run the tool.
3- Open Flashtool in C drive and place lock key in Firmware folder.
4- Switch off the mobile.
5- Connect Mobile to PC by pressing Volume down key.
6- Click on Power.
7- Select Flash mode.
8- Select D2502 and click on flash.
9- It will Wipe data and Mobile will be free from pattern.