Kotak Mahindra Bank — force closure charges

I am holding a personel loan account no.[protected] with the kotak mahindra bank ltd since aug 2015 and i had paid regularly our installment through ecs now today only 5 installment has balanced and i want to force closed my loan before march. But the management said we have to pay 5% force closure charges with 18% gst. I cant believe that i had paid 36 installment regularly and bank said give them such charges.