Inverter ****

Ordered an Inverter that was supposed to give 8 hours of power. Paid half up front R4000, Less than 24 Hours after plugging it in one of the two batteries Blew UP!. They came and swopped out both batteries. After charging the batteries to their specifications it only gave us 2,5 hours . They came and took it back to sort out, now they wont bring it back until we pay the balance of R4000. They also wont pay us back our initial R4000! They are ******!