Bad service

I have a one year old Samsung S5. It has now been to Vodacom 3 times in the last 3 months and all they do is reload a software update but the problem keeps coming back. Phone freezes, camera fails when you want to take photos, touch does not work properly and I have to pull the battery out to restart it. It has just been returned from their JHB branch once again and I was contacted to come collect. They only did a software upgrade again. According to my Consumer rights when a phone goes in for the same repair 3 times they are supposed to replace the phone. Why are they keeping on giving me the same broken phone and not correcting the issue by replacing it.