Terrible service

I upgraded on the 3rd of July 2017 to a Samsun J7 Prime. I have had problems with the WiFi on the phone as the Wifi just switches off automatically consistantly. The phone has been in for repairs 3 times already and the problem still remains. I was told there is nothing wrong with the phone and that it is only a function that is not working. Tomorrow will be 2 weeks after I have given the phone in for the 3rd time that it is going back again as it is still not working. My phone is now going in for the 4th time due to the same error. I have only had contact with the head of repairs Riaan van Wyk today after I complainted and said I will be putting it on hellopeter. But still I am just getting empty promises and my phone needs to go back to Johannesburg. I have asked to cancel my contract already due to this bad service as I am without a phone and the phone has been in for repairs more than I have had it and I do not trust the phone due to all the errors I have had. I now have to wait longer with no time given to me of how long it will take. I have been told I will get a new phone but that has not happen yet. Now it is that everything will be sorted by Friday but I have been told these things so many times and here I am with my phone still not working and sitting with Vodacom repairs department still. The branch manager and consultant have been so helpful and trying to assist me with this situation but they have done all they can.