Vodacom not accepting responsibility

Upgraded contract on 4 Jan 2015 at Greenstone, took handset to a Vodacom shop in Somerset mall on 8 Jan as the battery was lasting 4 hours on a new Samsung S5. I was advised that it was because Apps were running in the background. When I asked why the handset was so hot I was told that it was due to the temperature in Cape Town. On taking the device to Samsung Edenvale they advised that it was hot because the motherboard was faulty. On returning it to Greenstone they said it is out of the 7 day return date Numerous calls to Vodacom \customer care"They advise me that stores are individually owned and they cannot help me"