What if the bank intimates wrong EMI not sufficient to pay the loan within the repayment period?

Had taken an education loan in 2009, Loan had to be repaid in 84installments at floating rate of interest. Repayment started from Jan 12 to Dec 18. Bank intimated to pay Rs 5768 at 13.25%interest. I started paying RS 6000 since then, rate of interest only decreased gradually never fluctuated as per rate chart shared by bank. When interest decreased to 9.25%, even then I was paying RS 6000. Bank never revised EMIs. In Jun-Jul 18 visited branch and told them that we do not want to overpay and would like to fore close our loan. Bank intimated us that still a staggerring amount of RS 1lakh was outstanding. We lodged a complain how it was possible since we were paying more than the amount quoted by bank in the highest rate and the same amount even in the lowest rate and only 4-5months was remaining for the end of repayment period. Bank did not give any proper explanation. In Jan 19 bank gave a letter citing that the EMI of 6000 was not sufficient to repay the debts, it should have been started with Rs 6500. We told them that we were following the instruction of bank who told us to pay Rs 5768in written. But bank did not listen, they said since outstanding is showing,we have to pay the entire outstanding amount. We kept writting to different authorities of Bank, and refused to be penalised for their mistake. Bank on Oct 19declared me NPA and also sent a letter from advocate citing that we must pay the outstanding within 15days or face legal action. I have also complained to ombudsman but it might take time to resolve. What can I do if I am summoned to court? . As per our calculation we owe them 20,000rs more as per their real time EMI payment instruction which we are willing to pay, but not more than that. Pls advice.