MHR Infotech - Defective Refurbished Laptop

Refurbished Laptop HP Probook *** G*, paid **,***/- Within **-days of purchase the laptop stopped working. They did testing for a week and informed that the motherboard needs to be replaced and demanded additional payment. Later they stated the motherboard isn't available. Despite repeated requests, they have refused to provide either a replacement or refund for the defective product. They have yelled at me and pushed me out of their shop & stopped answering calls, leaving me without any resolution to this issue. I kindly request to investigate this problem and help me with a refund/replacement, as per consumer rights for defective products.