What is the use of a warranty.

I have a Samsung S7 Edge. Took it out on contract last year October. Unfortunately it fell and the screen cracked. It made a neat crack and i was happily still using it. Last month the phone started freezing and shutting down after being prompted by Samsung for updates all the time. We took it in for repairs and after a week we were told that we need to replace the motherboard costing R4500 before they will replace the screen as well. The manager at Samsung Canal Walk was not very helpful and said that the technicians will decide what is covered by the warranty. I am seriously not impressed with Samsung and will not consider buying a Samsung phone again.