Bank Charged Rs. 20000 in 2.5 year for paying Rs 36 Less in 1 Credit card statement Outstanding

Hello Gurus, I faced a challenge where I paid full amount except Rs. 36 in May 2015 statement and they charged Rs 994 in next statement. I called up the team and tried to get this reversed as this is almost 2500% charges being applied. They denied to reverse this and later i also left this issue opened and from then they started charging 300-800 every month for 2.5 years. Later in Oct 2017, they called me for this 18000 outstanding to repay. I simply informed them about this issue. The collection authority even convinced with this. But they told me that they don't have power to do this. As it operates centrally. Bank then put the hold in my savings Bank account for that amount and later debited the same amount. I followed up with them several times, but they denied on even listening that. What they simply say is that in May 2015, you were to pay Rs. 28801 but you paid Rs. 28764. So you will have to bear this charges. Now my question is that do i have any provision to get this amount refunded from Bank.