No delivery of goods

On the 20 April 2015 we agreed that the Stellenbosch glass center and aluminium company would supply us with 2x2500x1300mm aluminium sheets that would be cut to specification.. We paid our money and when delivery arrived were supp**** with the incorrect material. They took the material back and said that they under-quoted us and asked us to pay R6540 more . We agreed to do so , that happened on 20 April. They delivered a week ago but it was galvanized steel and not aluminium , I had the goods returned to the shop and we are still waiting for delivery of our materials. The owner keeps telling me he is on his way, but he never arrives.<br> I have asked them to refund me the money , they have not done so yet.