Faulty Samsung Vodacom Phone

I bought a Samsung Galaxy J1 Ace phone on 13 April 2016 at Game Carnival Mall. Within 7 days the phone would show that the battery is full, but within minutes would go off due to low battery. I could not take the phone back within the required 7 days to be replaced, as I was on holiday and did not have the box or proof of purchase with me. Nine days after I bought it, on 22 April, I took it back to Game to send to Vodacom for assessment and got it back on 29 April. The problem has not been resolved.