Samsung S4 wifi

I am a Samsung loving individual. I bought my samsung S4 Galaxy brand new from vodacom. 2 months down the line the phone was giving me problems where people would phone me and the phone in my hand will only say the number you have dialed is not available. When i took my phone to Samsung at constantia kloof they replaced the whole board on my phone. it happened again a few months later and the same was done. it had a problem with wifi they changed my board again. Now its doing the same thing and i am being taken from pillar to post by a mere guy at samsung constantia kloof. i wonder if i am getting this kind of treatment because i am black or why? my phone has always been fixed at the same place which is samsung constantia kloof from the time i bought it. I dont fix phones to put bread on my table i am an IT Guys. i am well ****ed off with how i was treated and i dont think i would ever buy a samsung product again. i even feel like selling all samsung products at my disposal because the treatment i got is so horrible i cant even believe it anymore. the technical guy tried to show me something i dont even know to make a comparison between my Samsung Galaxy S5 and my S4