Gentech inverter

I purchased a Gentech 800W inverter from Macro Alberton during December. The Macro salesman raved about it. Said I could have a TV and decoder on during loadshedding. From the word go I got no more than 20 minutes watching time. My Tower computer, 15 minutes. After being away and having the inverter battery on charge, I got same results. I took it back to Macro, the sent it in to Gentech. It came back with various stickers on, telling me that the battery needs 72 hours charge and that the unit is not suitable for loadshedding. Above schedule 2 there is not enough time between outages to charge fully. My question is, why were these stickers not on the outside of the box the unit came in. If they were, I would never have purchased . To me It feels like I'm being ********** by Macro and Gentech