finance charge

Hi Community, I had a SBI card bill of approx 42k generated. After 4 day of the bill generation a refund credit of 2100 was done from Flipkart. So I paid the remaining amount which was 40k finally. The total credit for the whole statement period became 42,100 RS. So the bill was fully paid...

I've been charged interest on standard charted card even though I made the payment within 3 days grace period but all in vain. I have even shared RBI guidelines with them but no gain. What can be done or if someone else faced same issue?

I have made payment of my ICICI credit card but some small amount was not paid by mistake and still I've been charged with 10k interest on my card, i.e. on complete due amount , is there any way to get the refund of these charges?