Lalela Invertors false claims

I purchased 2 x Lalela Invertors 4 months ago from Leroy Merlon, the salesperson and the literature claimed:20 Hours Laptop-8.5 hours Laptop + 2 screens-06 hours Desktop+ 1 screen -.05 hours TV + DSTV Decoder. from day 1 it never lasted longer than 2 hours just running a Medium Tv and Tv Box. when I contacted them the manufacturers, they informed me I would have to replace the batteries for more than I paid for the complete Inverter.