Won't buy back extra material he quoted me on

I payed for building has material from gbs bricks in laanglagte after I gave them my plan they did a quotation for me. They worked it out to about R30000 to build a single garage.i had to call and fight for each dilevery to Come and it was 3 deliveries. They had promised to bring material as and when il need it. That never happen they bombarded me with material I won't use at first. Now there is extra material worth about R4000 that I didnt use. They say they don't take material back. Please help get my money back. They must Come get their material back that I paid for. I need my money.