Returning of goods

I have purchased the tiles last year at Rooiwinkel. When I was buying I bought them under the impression that I was buying Harvey tiles instead the shop did not notify me that they do not have Harvey.they delivered Durex top tyilewhich is something similar to Harvey and me not knowing I ddnt say anything.now when I asked the builder to do the roofing he is the one whjo has notified me that it is not Harvey .I have purchased the tiles fgorR 27500.00. Nowwgen I want yo exchange to concrete the owner is telling me that he is going to charge me 10% if in exchanging and 20% if I'm returning. Yesterday they let me deposit R17620.00 in their account in case I'm exchanging and adding material only now they are telling me that they will charge me. Now even if I want a refund I'm being charged by the bank and this charges will affect my budget. Please assist me with this issue because the owner is very rude he dropped the phone on me this morning.