PaySense — Personal Loan -unnecessarily penalty charge by paysense

Hi,
I have taken PL 5 months back until last month everything was fine.There was issue in there App and one payment was delayed for a day which is paid by me very next day.To my surprise they charge me 2950 rs penalty for a day late.This month I saw I need to pay 8350 which was not clear to me hence i have sent them email for clarification but no positive response received and I dont have any option to pay only emi value hence I have hold this payment. but my surprise now the are asking almost 12k where 5900 is penalety charges.I am planning to file suit against them as it unnecessarily increased burden and impact my cibil by them