Harassment and Rude behavior from Sri ram finance Employees

I took a mortgage loan of 50L on my house from Sri Ram Finance on 25/11/2017. EMI is 152100. I am into business, So i couldn't honor the EMI dates but always used to pay within 15-20 days of the EMI date. To date, I have a pending amount of 1 EMI which is past 16 days. But every month these people come to my house and behave rudely. There behavior now became intolerable. When I was out of town this month, they came to my house, asked my mother to come out and locked the house and went upstairs and told tenants to vacate the property. They threatened my mother if amount not paid in couple of days they will come again and lock the house permanently. When i came back, i called the DM to speak regarding this. He is even rude than this Sriram agents. He started speaking abusively in vulgar language. I would like to know what right they have on my property as my loan isn't NPA. Even if it is NPA, can they do whatever they like without legal court order. When i told DM, you dont have the right to behave in this way, he said their company isnt a bank and said they have right to do so. He even added he will put a board infront of the house and will lock the property. My blood went boiling when i came to know what they did to my mother. I want to take action. Pls advice.