IDFC first bank - Unethical practices of IDFC first bank

Hi, I've availed personal loan of Rs******/- from IDFC Bank on **.**.****. After paying EMI for few months, i paid lumpsum of Rs******/- on **.**.**** after confirming from their customer care phone so that my EMIs can be debited from the lumpsum. So, till Nov **,my EMIs were debited from lumpsum. But all of a sudden, they stopped debiting EMIs and adjusted my remaining Rs*****/- to the loan tenure without any intimation to me. Then i raised a complaint with them to which they replied i should have informed them in written to adjust that lumpsum to part payment at the time of deposit itself. If that is the case, why did they adjusted my EMIs for * months and stopped suddenly without any intimation to me? They never accepted their mistake and alleged me. I asked them to give in writing or quote their bank policy where they can debit EMI from lumpsum for whatever months they can and stop suddenly without informing the customer. I said I'll pay EMIs if they give in writing. They never replied for this and only tortured me over phone calls. How unethical is this on bank's part? Since * months my issue is not resolved and my EMI is showing default now. Won't it affect my CIBIL score badly? I'm ready to pay EMIs but bank should accept their mistake, make changes to my CIBIL and apologize me for the gruelling mental torture. They should stop such unethical practices henceforth. Kindly help me.