I also faced a similar experience in Sharekhan, when they used to swallow up more than half of my profits and increase my losses 1 1/2 times
I am now with Zerodha and I took that decision after reading about them in this forum. @Rs.20/- per trade, their brokerage rates are amazing. You can get a decent margin for Futures too, approx 9-10K per lot:thumb: