Free 1500MB is available by dialing *537*2#.
Dial *56*8*23# to get 500MB for free.
Dial *7863*86# to get a free 1GB for one day.
Dial *117*111*2# to get 2GB of free Zong data.
Get a free 4GB for a day by dialing *568#*11#, *44#, or *102#.
Dial *563*85*23# for one week and get 1GB of Zong data.