Charge in delivery and handling is ridiculous

I am very disappointed in how these people treat me. I bought 3460 roof tiles from then. The house where they should deliver is less then a kilo meter from then office. They charge me over R4000 for the delivery. When i asked them why so much they tell me that they have to pay the people who is off loading and also the truck. Why is that my problem? Now I am returning some off the tiles that i did not use now they charge me 15% handling fee and i already pay tax twice, in delivery and in the purchase that i made. This is unfair and I believe that the ombudsman should look into it. The house where they delivered to is less then a kilo meter away from the house. How can you charge a person so much. I am really disappointed in the way how they do business.