Warranty repair - Bad Service

I bought a Acer A315 N4000 4GB laptop 500GB Blue from HiFi Corp on 18 May 2020. Since the beginning the laptop is shutting down by it self and restarting. It gives a rebooting error and reboots by itself automatically. I have booked the laptop in at HiFi Corporation on 5 October 2020 to get this problem sorted out. I need the laptop to work on and could not as it was faulty. I do have a 1 year warranty. Invoice number 1284. Serial number: NXHG9EA***A74S00. HiFi Corp phoned me on 16 October 2020 to inform me that Acer Africa claims that the operating system is damaged and that it needed to be repaired. It will cost me R1086.75. After our conversation where I said that I should not pay as the unit is under warranty, they informed me that this is not under warranty. If I do not pay they do not release the unit or repair it and I also will have to pay an rejection fee. How is this possible that if the unit is under warranty, that I should pay to get this fixed. I was not informed of any of this when I booked the unit in. HiFi Corp personnel just say they did not know. How am I suppose to know, if they do not inform the customer. And after all this unit is under WARRANTY!!!!!!!!!!. This morning, 17 October 2020, Danielle Woodington contacted me to forward the quotation from Acer. Again I was being **** to from HiFi Corp as they said the operating unit was faulty, and the quotation stated I am being charged for LABOUR AND DELIVERY!!!!!!!!!!!!!!!!!!!!!! How can I be charged for labour and delivery if the unit is under WARRANTY and they say the operating unit was faulty. How should I pay for this. This is unacceptable. HiFi Corp insisted it being repaired and cannot be exchanged for a new unit. HiFi Corp keeps lying about what the quotation is stating and demanded I pay. Otherwise I will sit with a laptop that is not working and still have to pay rejection fee.