Amazing and hot offer from Airtel in those days Telecom companies are introducing amazing and good offer to their customers i think it must be that they want get more customers in the race of getting more sells of voice and data.
But the offer is note for every sim it was only for selected some selected sims but any way you can try it and see if some can get it.
How to get free 200mb or 100mb from Airtel
Dial *123*189# to get 200MB or 100MB of yours.
200mb valid for 7days while 100mb valid for 1day