STS Turbo heat problem

Question

I have a Barbecues Galore STS Turbo 4 burner propane grill that doesn't regulate heat. High and Low give the same temperature on all four burners. The temp holds at 425 it won't get hotter or cooler.The store has stood me up twice on a promised service call. They schedule a service tech and he never shows. I am very dissatified with this supposedly top-of-the-line product and with Barbecues Galore themself.Dan B.