Angel Broking Brokerage on Penny Stocks...?

I have bought Surat textile @ 3.90 (Penny stock) & I have been charged Double brokerage. So, Will Angel Broking charge "Paisa per share" or As % on Total trade value. They have told my Brokerage as % on total trade value. But they charged to me paisa per share as If I purchased Penny stock. Is there any kind of rule to charge brokerage as Paisa per share if stock price below Rs.10 or something. Even i have proof of already written on Angel's Client master profle . What should be the correct brokerage As mentioned by Angel broking or They can charge with their own decisions...?