Samsung Mobile Phone - Loss of valuable time and money due to unreliable mobile

I bought Samsung M ** mobile phone in Mar **** and exactly after ** months, the company forced an automatic OS upgrade and automatically installed firmware and OS upgrades. After this , the mobile has started restarting on its own repeatedly. Since Aug ****, I had been approaching the customer care and the service centre and they made me land the mobile for checking and repairs at their service center on ** Aug ** and since then they had been giving al the reasons not to repair/replace with a new one, as the problem is due to the poor hardware and they are saying that the motherboard is required to be replaced alongwith power supply PCB.