Poor Service and Less Material Supp****

I bought building material(Plaster and Crashed Sand) from Cashbuild Vereeniging, they delivered less amount on both materials. I bought a total of 12 cubes and only got about 8 because the guy(Thabang) who was assisting me at the store told me that their truck can only load 4 cubes at the time. not more than that. My builder also confirmed that the material looks a lot less than normal. What confirmed my suspicions is the fact that the delivery guy was proposing that I cancel the transaction with Cashbuild and he will supply me. So how do one trust such behavior. I tried to ask the Cashbuild to send someone to come and confirm the delivered material and it never happened. Just be careful when you are going to be buying from those ******.