Bajaj Auto — loan amount

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Bajaj auto finance.

I have taken bike in a loan, and I paying Emi monthly before the date, some how after one month from purchase the vehicle.some one call from bajaj auto finance and they told Our bank account has rejected, so I asked them how pay our emi loan, they told u can pay by vadofone office and I done with the payment before date of emi in vadofone office, after 3 month exicute came at home and they told u have to pay panalty for cheque bounce in the bank from 3 months, and we have paid that amount.

I want to know that why should I pay that panalty which I have not made a mistake, ... I need a 100%sure answer
Loan number L2WBAN06179708