Shocking customer service

I upgraded my cellphone contract online with Vodacom in November 2014 and received my new, apparently, Samsung S4 mini via courier. From the start, the phone would reboot itself everytime I connected to the mobile data. On the 14th of February 2015, I took the phone into Vodacom branch and the had my phone for 5 hours, replacing the sim reader and doing a software upgrade. I had the phone back for 15 minutes when the same problem presented again. I took the phone back to the branch and they fiddled with the software again. While they were busy with it, the phone rebooted itself again. They then replaced the battery and gave the phone back to me. Over the next 5 days, the phone had the same problem again. I took the phone back to the branch on the 19th of February. They could not replace the phone, it had to get sent away to be checked. I received the phone back on the 27th of February and they had apparently replaced the screen. Within 10 minutes of receiving it back, the phone rebooted again. Now the phone has to be sent away again as they cannot auth a new phone. I am appalled at the fact that after 4 attempts to fix an obviously faulty phone, they cannot replace it.