Hyundai I20 Fluid 2012 Model review: overheating problem

Back in 2012 I purchased my Hyundai i20 fluid brand new from Hyundai Centurion. I had the car for 3 years at very low mileage (as I was only using it from home to work) when my engine overheated and seized in 2015.
The engine was replaced with a brand new engine and the car was fine till it over heated again 2017 and blew the radiator. The radiator was replaced and the car was ok until recently.
March 2018 it started overheating again. I took it to a Hyundai nearest to where I stay which is Hyundai Midrand where I was told that I need to replace the thermostat as it is the reason why the car has been overheating.
I told them its not the first time this car is overheating so surely there is a very serious issue that is leading this car to keep doing this.
I Dropped the car off to fix the thermostat and they said the head gasket cylinder is also busted thus I need to change that too which I will cost R10958, I agreed to pay that amount as was desperate to just fix this problem once and for all with a guarantee that I would never have this overheating problem again, this was on the 6th of April 2018.
A week later (13 April 2018) Hyundai Midrand has told me that they only realise now that its not only the thermostat and the head gasket that I need to change but I need to get a brand new engine again, mind you the engine I have now is not even 3 years old and that since my car's warranty expired 7 months ago (September 2017) that I will have to pay cash for this new engine (in-spite of the fact that, this problem that lead to this problem have been an ongoing issue that they have been aware of but have done nothing to truly resolve it whilst my warranty was still valid, they instead fixed "certain"components to delay the inevitable... And here we are!
Second engine in a space of 5 years! Wow...
What pisses me off is that even if they replace my engine right now they say they cannot give me any guarantee that this problem will not happen again, so really what is the use then?
I feel that Hyundai is taking advantage, they probably know the root cause of why this car keeps overheating but do not want to be liable to just say this is probably a factory fault, we can do nothing to fix!

Any one with the same car that has the same problem please let us unite and expose these people!