unfair payment

I open an account at Build it for building material in Randfontein but Real people have been debiting money from my account because they were the money provider. The contract was for Real people to debit money ( R14.444.74) for a period of 24 months. From January the money was debited from me for a period of 10 months instead of 24 months because the shop (Build it) was shut down. So i called the lady who use to work at Build it concerning my money because i was given a credit of R19.422.42 and i used only R770.76 from that credit. She said i must call Real people for my refund, I called them and i got paid an amount of R3.660.35 from R14.444.74 that i paid for the passed 10 months. I asked how come i get so little money, they said it's interest. But what i did not get was interest for what because i did not even take material for half of that money. so this means i lost R10.000 for material that i did not get, Build it paid Real people their money back so why can't i get my refund in full because i am not responsible for the closing of the shop. And this happend last month(November).