So Disappointed!!!

I bought a samsung core 2 SM - G355 white PP on the 15th of April 2015 at CNA Shelly Beach Centre. It worked fine. last month it started switching itself on and off...not once, not twice, not three times but more than 10 times a day. I can be typing or on an active phonecall and it would just switch itself off. Now can i get an explanation why is that? coz i dont even have alot of Apps and i even deleted some but its even worse in 5mins it can switch off and on 3times.....today is the 2nd of June, this phone is LESS than 2 months old but ALREADY causing drama !!! I can't deal. Its pathetic and i actually trusted this brand!!! :( really disappointed ! Never again!!