Devy Glass Hop not working

This is My fourth Complain for the same Glass Hop. Plates not working ,Glass heats up and switches off automatically after 1hour. The senior technician (Mark)came out to declare the hob Useless. After 4 visit for the same stove. Two weeks after I am still without "the glass hop" Cooking on a one plate gas stove for family of six. Head office phoned but they even more *********** than Johannesburg Branch. Invoice was send to replace Hop but to no Avail. They dont care about their Customers at all