Faulty Acer Aspire 3

I bought an Acer Aspire 3 for Telkom in contract in February. The device has been faulty ever since it came out of the box. I've sent in the device 2 times now but the manufacturer insist there's no hardware damage. The device is extremely slow and constantly freezez or goes blank. I continue to pay for a device that isn't usable.. It's the third time that I've launched a complain and I'm going through the same process of sending in the device again.