Amazon India — Mis selling of moto g turbo

Address:	Thane, Maharashtra, 400601
Website:	Amazon India

Recently a promocode was been floated in all the social media which allowed the user to avail a discount of rs.7500/- and pay just 4, 999/- as against its original price of 12499/-.

Amazon has accepted the promocode & accepted my payment of rs. 4999/-, they confirmed my order on 27th march, 2016 & sent the delivery confirmation as 31st march, 2016 via email. But all of a sudden at 28th march, 2016 i recieved a mail stating your order was cancelled & the refund will et another 4-5 days to credit the orignal payment mode.
They are on the stand that the promocode was technical glitch & amazon is not responsible. In that case i asked them to refund my money immediately but they are like it would happen after 6-7 days from the order date. Who has given the rights to amazon to use my money without paying the interest. Also i feel that due to 31st march, 2016 they wanna show inflated balances in their balancesheet so they making this kind of fake promotion.
Kindly help me in getting the mentioned product or my refund amount along with penality.