Standard Chartered Bank — being charged a4 interest

Address:

445 lake gardens . Kolkata 700045, Kolkata, West Bengal, 700045

I pay my minimum dues in my standard chartered credit card on a monthly basis. And that too in time. Yet i see the amount is staying similar which is pending and then i check details i see a4 interest being charged on my credit card every month. Why would i unnecessarily pay this fine? I had bought a product for which i was paying in installment which i gave way on time so no other interest should have been charged. A4 interest as i read is for late payment and all. Please resolve this. I end up paying more interest than credit.