Firstly, you have to Analyse and tweak/change your IMEI to this IMEI number 359838075475772
Tweak the last three or four digit
Download Mtk engineering mode and IMEI analyser from playstore
After that, dial this code
*8186*092840413028038# up to 10 to 20 times.
Then you will receive this message saying ” Congratulations! Your free 1GB data has been successfully activated, data is valid till -/-/17.”