Bajaj Finance — penalty charges

I feel like bajaj finance is a cheater...
My loan emi starts from march 2018 and ends in october 2018...
Some months i made late payments and they charged me extra 400 rs for each loan account... I have 2 loan account so i pay 800 some months...
Now since september i started getting calls and messages saying that i still needs to pay penalty charges... And let me tell you i have 2 loans and i made payment for both loan together... Why bajaj people asking me penalty payment for only one loan account.. Y not 2..??
And executive who calls me don't have manners to talk... If there is penalty for bounce charges why didn't they tell me since my first emi or in the month i paid late emi... Y are they telling that when my emi was about to be over...???
Please check on to this i am not responsible for any penalty... Coz i paid late payment charges whenever i paid late...