Samsung S6 worst phone ever.Never mind the service

I upgraded my vodacom contract on the 1st July 2015, with a Samsung S6, this was the worst decision I ever made. Within a month the phone started lagging, I took it to the Samsung shop in the Somerset West Mall, and was told by the technician, that they needed to do a software up date, which they did. I lost all my music, pics and most of my contacts. Result - nothing still the same. I then took the phone back, I was then told that they had to do a hardware update, the phone would have to be sent in. Let me at this point explain, that I run my own business, and the phone is my contact with my customers. I insisted that I wanted a new phone, as this problem should have been sorted out, before my upgrade. Three months later, after emails, and calls to Samsung, they replaced my phone, yippee, I was a very happy....until yesterday around 15h00pm, when completing a call, my NEW phone, goes black, and I cant do anything, no calling and receiving calls. Hi ho hi ho, its back to Samsung I go, with a technician, that has attitude like really, and was 25 minutes late for work, but not too worry I have my own business. The phone is now in for assessment..I WILL NEVER BUY SAMSUNG AGAIN EVER.