failure to comply with consumer protection act

After receiving a defective phone with software issues affecting all devices of the same model... I attempted to return the phone, but alas! Since it was ordered online, no store would help me. Convinced MTN was sending me through a myriad of bureaucratic hurdles in order for the 10 day cooling off period to lapse and trap me into the contract, I endeavoured to make my case at the head office. By this time I was so fed up that I decided I would cancel the contract altogether, knowing I could do so because of the cooling off period as per the consumer protection act. Here I was told that I would be forced to pay R13 000 upfront if I cancelled the contract regardless of the cooling off period (which the consultant was oblivious to), however I could submit the phone for an OBF (out of box failure) and receive a new one of the same model, but the consultant offered no recourse for a systematic failure of all devices of the same model. Fearing an endless cycle of failing Lumias and subsequent returns, but being trapped in the same contract, I wonder: does the Consumer Protection Act oblige MTN to replace a faulty device but allow them to entrap customers indefinitely ( from day 1 of signing a contract) or am I entitled to cancel the contract within an agreed cooling off period regardless of cause?