Cibil getting down because of penalties

Hi everyone, So I have a serious concern, I had a loan going on with Kotak which is down but what exactly happened was my second last payment was late my a day, I got a call from a recovery agent or idk who from the department and I told me to make the payment via going to paytm and searching Kotak loan and making the payment from there. I asked him multiple times if there would be any penalty if I make the payment like that and he said NO. But I got the penalty of 750 on my loan account. I tried calling Kotak customer care but unable to connect with them so I intentionally delayed my payment because they will call me and I can share my concern. It happened, I got a call from them and informed the exact scenario. That guy assured me that he will remove those penalties and make sure that no further penalties being charge for this payment. But nothing happened and got a penalty of 750 again. Making a total of 1500. I contacted bank multiple times and I even mailed them as well stating that “I do not have any problem in making the payment, but I want to do the audit of the call which I had and share the same to me aswell if possible, if there is any fault which lies in me. I will make the payment straight away. But I will not pay any amount if it is not my fault”. Bank is not helping me in any possible way and stating that I have to make the payment. And now I got a call stating that if the payment is not made my cibil will be affected and all. Can anyone tell me who can I drop a mail to who can help me with this? I really need it. And yes the penalty is not because of late payment, the penalty is because I have made the payment from the third party application which is paytm. Problem is not with the amount, the thing is that in future they can put a penalty of whatever amount and threaten me that my cibil will be affected. And this is not right at all. Your help would be highly helpful to me.