Is Demat account in Stock Exch. advisable?

#1
I heard that charges for maintaining in (Madras) Stock Exchange is cheaper ie. Rs.300/- as compared to Rs.400/- charged by others. Other service charges are also reasonably cheap and no hidden expenses. If any one having Demat account in Stock Exchange, can they share their experiences and pros and cons. Though I am having an account with a private DP, I am not satisfied with their charges...... tks......