Sometimes, because of technical glitch, customers end up paying twice for same order in which case Myntra needs to refund the one amount. So if you have ordered something on Myntra and got double payment done for same order, you can complaint about that to the Myntra payment complaint service.
You will have to provide reference number of payments and order number in which case you will get refund for double payment on Myntra.
Here is customer care number of Myntra for double payment complaints
Phone: +91 80 4354 1999