Ridiculous quote for main board replacement

I've had my Samsung Galaxy S5 mini for about 4 months and I love my phone. On Monday 29/06 my phone did an automatic software upgrade as usual but on Tuesday 30/06 my phone suddenly started restarting itself over and over and over. I did a factory reset because I thought it might be a faulty app that caused the problem. No luck. Took it to the Samsung Store in Boksburg and they say it is the main board that is faulty and that it isn't covered by warranty. They charge me R1 629 to replace and say it takes between 5-14 working days to get done. I'm really upset by this since the software malfunction that caused the main board to get damaged is not my fault and a manufacturing fault and should be covered by warranty. I'm a big Samsung fan but am considering moving to Apple iPhone because of this. At least they will give me a trade in discount for a new phone too.