ICICI Bank — unauthorized debiting from saving account for cc bill that was paid

This is regarding my credit card bill.
The initial bill was 35920/- for which the payment was made before the due date. I have proof of payment and all other necessary documents.

However i have been getting calls mentioning the bill has not been settled.
I have talked to multiple individuals and sent email but to no avail.

Now there has been a debit from my account for inr 3730 toward interest on the outstanding. Why are you charging for a bill already paid? Who authorized this transaction?

Can anybody let me know what legal options i can pursue?