product sold still in warranty refuse exhange

07.08.15 Game had a promotion on 2 Sinotec Tablets for the price of 1 ....i bought the tablets paid , but there was no stock , stock was only received 19.08.15, the one tablet just went blank on 17.09.15, wont charge wont switch on , i called the store spoke to Nolan who advised i must bring it back with all accessories. i went to the store on 18.09.15 spoke to the lady at cust care who called Nolan who advised her telephonically to give me a voucher of R500 which i can choose a phone with , i refused as i had the tablet less then a month and it just went blank , they tested it instore as well the salesman advise that these tablets is problematic as it comes back all the time, they then decided to book the tablet for repair & i must wait 22 working days for a response . Now is this tablet not still under warranty ? they sold a product knowing it will be a come back now they offer half of what i paid coz i did not bring in the other one that is functioning & i waited for the stock almost 2 weeks now i am sitting with a dead tablet that i still have to wait for 22days ...this is unacceptable