Zest Money - Asking me to pay extra

I have taken loan of **,*** from zest money on **th November ****.
I have been told that Rs. **** for * month will be auto debited on *th day of every month from my account.
I have been asked to maintain sufficient balance in my account and I managed to maintain balance in every month. But they failed to auto debit emi ammount from my account for * months and suddenly in *th month they auto debit my account with Rs ****.
I called customer care and asked why my emi is not auto debited on time and when it is debited then why Rs **** is deducted. I have told to pay **** only.
Customer service agent told me that due to technical fault my emi is not auto debited and the issue ia resolve. Now i will also receive cashback of *** every month.
But i didn't received cash back, i again called zestmoney regarding my cash back. They come to me with irrelevant answer, they said i didn't have money in my account that is the reason my emi is not auto debit and due to this i will not be able to recive cash back, and now they are forcing me to pay huge penalty of ****, even though when there is not any fault from my side. I have maintained the balance in every month. My bank statement is attached with the complain.
I request you to please help me clearing my loan with zest money and please save me from this huge penalty of Rs **** and the mental harassment which is being done by zestmoney to pay such huge penalty, because there was no any fault from my side.