Faulty Product

I bought a Samsung Galaxy Core Prime {SM-G360H} at CNA Shelly Beach on 29 May 2015. Since 08/11/2015 it was faulty and were sent in for repairs three times. On 08/11/2015 to Durban Hub. Then on 28/12/2015 to Vodacom Port Shepstone. We received it back and only two days later it was taken back and was sent back to Durban Hub on 05/01/2016. We handed it in at CNA with all the accessories including two batteries. It was in for two weeks. After which they informed me that they can't repair it and it was taken off warranty because they found liquid damage on the motherboard. I deny that the damage was caused by me. When I received it back, there were obvious signs of water damage. These marks were not there when I took it in. I have two witnesses who helped me with the battery just before I took it in. I received it back without either one of the batteries that accompanied it when I handed it in. I phoned Durban Hub and the assistant admitted that they will send the battery, but only doing that will not be to my satisfaction. I demand a replacement of the phone and my warranty must be restored,