Myntra.com — Myntra has charged me more than MRP

Myntra nowadays are cheating their customers by charging more than MRP. When i asked them to refund me the extra money they charged, they said they won't. Rather asked me to go the through hassle self-ship the product.
I told them that i don't want to return the product because there's no issue with it, i just want them to refund the extra money back. But they denied to.