unhappy about poor service

My name is Vincent Anderson and I would like to lodge a formal complaint about the very poor quality of service rendered by Rosettenville cash crusaders. On the 18th of January 2016 I returned a faulty cell phone and proceeded to add a cash difference and then bought another cell phone. The first one I purchased for R650 and the second one for R1500. I erased the device in store in front of the sales person then updated it with new software using their WiFi. After using it for two days I noticed this device was also faulty. I took it back on the 20th only to be told by management that I must choose another device or something else to the value of R1500. There were no devices to my satisfaction so I asked for a refund and was refused. On the back of the slip it states they will refund, replace or repair and as repairs will take too long and they couldn't replace to my satisfaction refund was my only option yet I was denied and I find this absurd. R1500 is a lot of money yet I'm stuck with a faulty device. It has many issues that I'm not happy with. I have been given the run around every time I go try to see the owner and fear my 7 day will expire, what can I do? Please help!