Bajaj Finserv — Bajaj Finserv grievances

I had taken loan from Bajaj Finserv in 2012, then of amount Rs20980 LAN401BAL00245415.
I had paid all dues and interest then. There was some non payment bounce of Rs260 and there was mismatch of signature in PDC. I received only email on 21/03/2013 the last mail that all my dues are clear.
But Bajaj Finserv has added grievances for each day till 23/11/2018 and I received email that I have to pay Rs15797.
Bajaj Finserv was dormant till 2018 from 2013. I had no idea of this amount. How can Rs 260 become Rs22535 on 05/10/2021.
Bank had not informed me of bounce.