Bad service...horrible service

On 05/04/19 we went to Hifi corporation in Mabopane and spent just over R 33k amongst the purchase was a LG home theatre (Sn 901h2q263020) and the item stopped working around October which I went n hand it over.There no communication from the store till November so I decided to visit the store...on arrival I was assisted but the lady in customer care whom referred me to the manager but it was not any help because I was told that in over 30 days the item was not fixed n was not going to be fixed as they it doesn’t have a serial number...so must I throw my 10k due to it not having a number I know non of?...I feel like the manager could have handled it better I mean this is why we normally shop in stores around town because they know the value of customer service and satisfaction ...