Samsung Phone keeps rebooting

A Samsung Galaxy Prime plus was bough as a gift last year, I have been battling to get this phone working for the last month now.

I have been to the Samsung Store in The Grove Mall Pretoria, and the tech worked on the phone.

Basically the phone reboots on its own on random intervals, they have done software on this phone and the issue still persists.

Im begging, I will go into another Samsung store to get assistance, Hope they can sort this out once and for all, or replace this phone with a working one.