Flipkart — Order not delivered since 3 weeks and not allowing to cancel

I ordered a product from Flipkart on[protected]. It was supposed to be delivered in 4-5 days whereas it has been more than 3 weeks order has not been delivered and there is no update on the delivery progress after[protected]. There is also no option to cancel the order. since I have bought the product from somewhere else I don't need this anymore. I complained through social media but still they couldn't cancel the product after ensuring that they will get it cancelled. They have again assured that they will get it cancelled but it is very unlikely. They tend to have this pattern often. I am also worried about the refund as this was a prepaid order.
Order No: OD[protected]