Myntra.com — My purchase converted to EMI without my knowledge/ consent

Address: India

Website: Myntra

I had purchased some garments worth around Rs 6800/- in March and I paid using my credit card!
I expected to pay the entire amount but to my surprise I found from my credit card statement that these purchases have been converted to EMI! Upon inquiry my credit card people claimed that the request for converting to EMI came from the merchant, Myntra in this case!
I would like to know why Myntra did this without my consent and if they did not do this, a confirmation letter to that effect!
Thanks and regards
S Muralidhar