Customer Right Refused at Pepstores

Bought a Hisense U40 handset the 24th November at Pep Branch 725 Town Centre for my daughter as a gift. After using the handset we discovered that the phone gets extremely hot. When I returned the handset yesterday 2 days before the 7days. The lady Kelly tested the handset and found the same fault. She then said she can exchange the handset but I cannot get the same Hisense again as if it gives problems it will be a loss for the company. Be that as it may, I have the right to choose what I want when I come and exchange. She then went on about how the prices are going up etc etc etc... When did Kelly purchase Pep, and I'm pretty sure that Pep is covered in instances of Obf handsets!!!!?!!!!!!!!!!!!!!!!!!!!!! DISCRIMINATING MY RIGHTS