Kotak Mahindra Bank — EMI Cancellation request

I bought an item from amazon but it didn't reach me and I went directly for return, and I paid through kotak bank credit card, but I reached kotak bank many times to cancel the EMI but they didn't let me. They say we can't do it. But if my EMI amount has gone back to their account then why won't my EMI get cancelled? This is what I need an answer to.