Icredit — Asking for more payment after paying dues

I was having a LOAN from ICREDit 2years back and suddenly today they start calling me and my relatives and random CONTACTs from my CONTACT list. Although I agree to make a payment and decided to pay Rs. 5000 to clear all dues. Then they shared me payment details to make payment..but when I tried it gets failed due to error from their end. I shared same with them and then after half n hour they again send details and I make payment successfully. Payment details shared with them and then suddenly that lady start asking for more amount of Rs. 2895 saying that amount change due delay in payment. What nonsense is that. When I refused again that ### lady started threatening me and harassing me