DP charges

I have account in one of the brokerage firm of india , i want to ask something about DP charges ,
i have some doubts regarding DP charges ,
my 1st doubt is i hold shares of many company in pool account of that brokerage firm , since last 1 year , but last week when i transfer those shares to my DP account that broking company charges for it .
my 2nd doubt is since last 1 one year i found demat transfer charges if i sold any one of my stocks from pool account of broking company ,
ex: suppose i bought 5 shares of sbi on 5th jan 2012 and i sold that sbi shares on any day lets say on 12th of jan 2012 that brokerage company charges rs 6/- against DP charges ( at that share was in pool account ) then why they charge Demat charges

thanks

deepak