Faulty Samsung J1 Cellphone

Good day<br> Two weeks ago I went for an upgrade at the The Glen Cell C shop. I upgraded to a J1 Samsung Galaxy cell phone. After two days of using the phone I realised that there is something wrong with the phone. The screen keeps on flashing, as if there is a short circuit on the touch screen of the phone. I took the phone back to the store, and they told me that they have to send it back to Samsung. After a week I called, and they said to me I can pick up my phone. They issued me an identical phone and once connecting it has exactly the same issues as the first phone. I went back again to tell them of this issue, and explain the situation to a consultant. Once her reply was not satisfactory I requested to speak to a supervisor or head office. She called the supervisor (Mr Reddy) but he suggested to her that I should phone head office. My new contract is 2 weeks old, and I have to sit with a phone that is not working for 2 years!! And as I understand from head office Cell C, they knew the J1 is faulty, but they still give it out. Can anybody please assist me on what I should do, as the Glen Cell C is unable to assist.