1. Activate 3g by sending 3G to 121
2. Recharge with Rs. 8/- for 8MB 3g GPRS
3. Then recharge Rs.15/- for 500MB 2G GPRS plan or any other 2G plan who you wana use
4. And Now enjoy 508MB 2G data with 3G
NOTE: Validity of this trick is only for 24 hrs.. Means till the 3G pack active you get 3g speed after that again you get 2g speed.And it only works if your network support 3g.
AIRTEL 3G SERVICE IN 2G PLAN