Boulders Paid but not received

I recently purchased very haevy Boulder 0.5 to 1 meter from ''Simon'' at the Pta/Jhb branch of Pavementmaterials Group. Full payment was made December 2019. Delivery was arranged early January. 6 Boulder was ordered. They arrived with 4 boulders ( Actually three and a half ). Delivery truck arrived late afternoon with only a driver. No offloading personell was present. Offloading the stones was impossible due to the weight of the boulders. I have all email correspondence of communication with ''Simon''. I have sent follow up emails for arrangement of the delivery. ''Simon'' denies that he received the emails, although I never received any email confirming that mail was not delivered. Simon continues an agressive form of conversation over the phone. He refuses to give me details of his superior, in order for me to escalate the matter. He has put the phone down in my ear on 2 occasions. He has R8000.00 of my mony anf I have no Boulders, and I fail to arrange any form of delivery from him. Unfortunately the only contact email and telephone number on the website goes to him.