VODACOM : Defect iPhone

I took a contract with VODACOM and been having problems since day one. I contacted VODACOM and they mentioned i should run an update, which I did. Since then defect after defect which then I booked it in for software repairs. Which is known as VODACOM (ARC) CENTRE which my repair number ***4 was sent to me? 10 days later I received the unit returned to me. I then used the unit for a day and still same problems. VODACOM sent a request that I rebook the phone for software repairs as to my knowledge was the case prior. It was resent back to the ARC for the repairs. However this time the repair centre replaced my screen which confused me why is VODACOM ARC replacing as it, as there was nothing wrong with the screen but a software defect. I received notification that my mobile is ready for collection. I contacted the consultant with an email that I would not take occupation & request that the mobile is replaced as the current unit has too many defects. Since then it has been 4 weeks with all these defects and I'm paying for something which is not in my possession. The latest I received was that its currently sitting with VODACOM (MFTR). This is unacceptable!!!