Shocking service

I got a Samsung S5 mini phone in September 2014 and have experienced issues since I got it. The phone turned off on its own. Never allowed messages to come through. I would have to manually swich the phone on off and on to get messages to come through. I have driven to the Fourways branch twice and was told it was software. The phone was repaired but continued to experience the same problems. I have since been to the Vodaworld a further 4 times to have it repaired again and again. My phone was finally replaced with a new Samsung S5 mini on the 30 March. My phone continued to experience the same problems as my previous Samsung S5 mini. I drove again on the 18 April to have this problem sorted and spoke to a Manager who said my phone would be replaced by a new Samsung model or I'd be credited for a new phone. I was promised a call on the 21 April. I have had no contact and have no idea what is happening to my NEW phone!<br> The service is shocking and I want answers<br>