Short change????

I placed an order for 4 cubes of river sand.. when it arrived, I queried the small load. No one was available to talk to me so I refused to sign the delivery note. Went and purchased 2 cubes from another supplier. When it arrived it was more than the supposedly 4 cubes from Build It. Again i called, again no one available, have left messages! They owe me about R800 Bac****