Repaired phone comes back with different problem

I received my Galaxy S6 from Vodacom mid 2015 just after they were launched. A few months later, in Oct 2015, I started experiencing serious issues with WiFi showing connected but not working at all. Then suddenly the phone would randomly reset itself until it was eventually in a continuous loop and completely unusable.<br> Vodacom in Bayside Mall (Table View) booked in my phone and sent it to Tyger Valley for repair in Nov 2015. I had to wait weeks as they waited for parts. Got my phone back in late Dec 2015. There was a list of replaced parts, INCLUDING MAINBOARD. When I collected, we checked that the problem it went in for was resolved, but when I got home I realised that I was missing calls, as now the sound/speaker did not work at all.<br> I then took the phone to Vodacom in Canal Walk. They ordered a replacement speaker and I had to wait weeks again for the part. However, when the part arrived and they opened the phone to replace it, they discovered a PROBLEM WITH THE MAINBOARD. The phone is now with them again, waiting for the part. Did Tyger Valley put in another faulty part or is Samsung to blame? Who knows? I want my entire phone replaced. Can't work like this.