Instead of going for branded brokers or their franchises/sub-broker, there are many who are unbranded and offer lower brokerage. I know a broker in Thane East who is offering 3 paisa intraday single day without any advance or commitment of turnover. But beware of the downside, they do not have full range of services.
Therefore, stay with a slightly expensive broker if you expect to be served good.
And if your volume is great, there is a great chance that your existing broker will himself reduce the brokerage. I know a member here who got brokerage of 1 paisa from India Bulls, but bear in mind that he has great volumes and it makes good money for the broker too.