Bajaj Finserv — After Paid All The Loan Amount, Misplaced Charges on Loan Amount,Also Continuously Putting charges

In 2019 we taked smartphone on loan, we have paid all the loan ammount before at the correct date, but on that time we didnt know about that we have to maintain that installment ammout in bank, because any of from bajaj finance does not told about that we have to maintain that loan installment in bank, we have paid all the our loan installments before the date of installments with the bajaj finserve, mobikwik app with that every installment has bounced almost all, that all bounced charges also we paid from the mobikwik app that they installed in my phone, suchwise we paid all the our loan ammount and having all the reciepts and also they provided me the digital NOC from app but they continously putting charges on why i dont know, at the current time they said to pay Rs.4950/-,

from the branch visit the officer told me that you have to pay of Rs.4950/- charges to close the loan,
and also after the discussing about our issues he said me to you have mistaked about you have paid your loans from online so you have to pay this rest ammount..

we are from the verry poor family also we are not able to pay like this much charges or ammout to pay, as in our family we all are dependent on my father who is working as watchmen, so
please help to us on this issue...