Standard Chartered — Credit Card installments were paid on time , still I am charged late fee

Address:

Thane, Maharashtra

I own a standard chartered credit card, and I availed emi facility for a purchase of 35000 approx for which I paid emi online timely every month.
But still after the last installment is payed, they are asking me for a late fee, saying that I payed on Credit card bill and not loan bill.
They have a complicated way of generating statements, and making payments, and they penalise and harass users for their own flaws.

I am being asked to pay a late fee, even though I have payed bills on time..