Zestmoney — EMI not debited on due date

My EMI of 3150 was due on 29/01/2021, when I tried to pay it on the due date using the app it did not allow me to pay saying that auto debit is in progress. I had sufficient balance in my account. When I checked it the next day it was saying that my EMI is overdue but it was still not allowing me to pay as auto debit was in progress. I contacted zest through call and mail and they assured me that no late fine will be charged and my credit score will not be affected. They did not let me pay nor did they auto debit my EMI for the next few days. When I checked on 03/02/2021 I found that the EMI was not debited and auto debit was not in progress. I immediately tried to pay and found that they were levying 250 rupees late fine with the EMI. I paid the whole amount including the fine as I did not want to be more late. I am very disappointed with the service of ZestMoney and demand that they return my late fine back to my account as it was not my fault (I have paid all my previous EMIs before due date). I also want to know if my credit score is going to be affected for this and if there is anything that can be done to fix this.