Pep stores do not help people who pay for products and loose their slips?

I brought a cell phone a week ago at Sophiatown PEP and the phone is faulty. I went to the shop on Monday and they told me they can't help me, even though I have the box and bar code. Then I emailed PEP stores after that I have not received a response. I then called their call centre and the women told me they can't help me. I feel ****** and the lack of help is ********* and ******* as I have proof of payment for my purchase. Can someone from your legal office call me on *** within 24 hours or else I am going to the Ombudsman.