Sony experia discertified with your products

I bought a Sony experia M5 from MTN in Alberton, about 2 weeks ago. After a week I started experiencing problems with the phone. I called Sony care Centre they referred me to they repair Centre in BARLETS. Took my phone for repaird, but I'm still experiencing the same problem with the phone. The phone just shut down by itself even if the battery is full. I'm totally discertified. Cause I've had this phone for less than a month. Please kindly respond via email cause currently my phone is useless... [Email Removed]