Bad service

I bought a laptop at Cash Crusaders Mega City,found to say it didn't have certain drivers, when I returned it I was told I'm going to pay money for windows, then they decided not after I will pay and will request a receipt, they decided to fix at no cost,only to damage the laptop further where wifi and sound is deadThey failed to replace it and told me where to get off,they are now saying the laptop is at the Indians to be fixed,I'm now struggling to my assignments and school work which pains me so much.