Sbi Credit Card - Excessive finance charge and that too without informing

SBI credit card charged more than **,*** Rs as financial charges & IGST from me from the past * months. I'm a person who pays the full due amount without pending single paise while my earnings are only around **k per month. I noticed it only this month when I tried to pay my bill which was higher than the usual amount, but when I opened the statement and saw the transactions, I got shocked that each month they have charged around *k for financial charge and *** for late payment and some *k for IGST. I request you take some action against it. These charges are very huge for me. When I called the customer care and questioned for this, they were saying that these charges are because I paid late. But I haven't got the due bill amount and date in the SMS for past * months, which is why I didn't notice the due date and paid late but I paid without a single paise as a pending amount.

I told them that I haven't got any SMS from past * months from/before January to pay the credit card bill, they haven't responded correctly, but I traced back them and ask them to hear what I'm saying. To speak truly, I haven't got any call from them to pay the bill on the due date for past * months before January, at least they should have sent text messages about the credit card bill amount and due date, but they did nothing. I have proof that I haven't got any call from them, I have attached the charges they put on me. The staffs that I spoke so far were behaving very rudely as If I'm using their money when I pay the full amount without arrears and treating customers as beggars. Apart from all of this, if they can send so many notification SMS for even *rs transaction, why can't they send a notification SMS for such a huge amount, like they are sending for other transaction. Finally, after several followup and complaints, they have refunded a small amount-*k, and that too I have called them and was begging. I'm ready to pay the full amount that I have used so far. Please get my amount back and take necessary action against these kinds of fraudulent activities by these banks and call me I can provide whatever proofs you may need against it.
Card no: ****************