Hello... I have bought a new galaxy s duos 2 a month - TopicsExpress

Hello... I have bought a new galaxy s duos 2 a month back. It frequently hangs and randomly switches off. When the lock/power button is pressed the phone becomes un-responsive and a reboot is required to start the phone again. Already been to the Samsung Care centre in my area. They took my phone and gave it back to me saying the had fixed the problem. But there is no visible difference in the phone. It still hangs. Still becomes unresponsive on locking the screen. Tge interesting part is that the phone never becomes unresponsive while it is charging. Please fix this issue. Is it the 4.2.2 firmware or us it just a hardware problem can you specify. Waiting for a reply.