Knock offs

Cash crusaders Vosloorus. I bought a wireless keyboard and mouse. R209. The batteries in the mouse died, and when I replaced them, the mouse broke. Led sensor light , the slots, everything was broke. This was in August. When I went to report the incident, they told of the 7 day period of return. But now, the batteries will never last me 7 days. The problem wouldn't have occured within 7 days in any case because the power lasts longer than 7 days. I stated everything, but all they could tell me was 7 days thing and that they can't do anything. Above that I tried getting their head office number, the guy told me about the website. Basically I had to the mouse with their batteries only, after that, it's done. What can I do