No network on contract sim

I've been with Vodacom for quite some time now and never had any problems with them, up until I bought the Samsung Galaxy s6 edge with them through a contract. I never have any signal, my calls cut and using the data I pay for every month is impossible. I've called them and gone to their stores countless times and they reffered me to Samsung, Samsung ran tests on the device and even inserted a prepaid Vodacom sim card into the device and to my surprise the phone worked.<br> I didn't leave it there as I thought the problem was with my sim card so I went ahead with a sim swap but the problem still presists, and the worst part is that NO ONE can help me with the most basic of services that I am PAYING for.<br> This is both shocking and disappointing.