Poor quality sound

I bought a home theatre on 29/08/2019, once plugged in on the same day the speakers were making a funny noise. I went back to the store spoke to Fisto and Tshepo and they made me listen to the same product which was displayed @ the store and they said those products have the same problem but there's no need for repairs. The amplifier is now not working hardly 3 months after the purchase. I took it to the store but could not provide them with the receipt of the purchase and they said they cant re-print the receipt (I gave them all the info of the purchase i.e. amount paid, date and time of the purchase).I escalated the matter to their head office and spoke to Xolani, his resolution was that I can take the goods to the store but if anything needs to replaced on the goods after the assessment I must fit the bill as its now out of the warranty since I don't have the receipt. I am no happy with the service having lost R3000.00 for something that only lasted less than 3 months. I want a refund or goods must be exchanged (I'm not happy with any repairing)