The worst company i have ever dealt with and i advice that just buy the material and not ask them to install

I approached this company in Midrand as they were selling paving slabs and i wanted my yard to be paved and the price for the slabs were reasonable . Was happy with the quote and i then ask if they can do installation and they confirm they had a competent team and they quoted me and i was happy. The day of delivery they were late and had countless excuses why ,i let it slide. On the day of installation the same excuses why they are not on time which i let it slide. I was advice that the paving can be designed differently and i opted to have peebles stones . They did such a terrible job which i complained and they refuse to come back so that they can fix their mess . I offered to even pick up their boss and i got an email indicating that they are not interested on my dissatisfaction i can seek counsel if i want to. I have paid this company R 36 090.00 out of R 39 290.00 and indicated that i will pay the balance of R 3 200.00 when they have inspected their work and discuss a solution ,they refused. On top of that they are refusing to give me an invoice on the payment i have made and they are soo rude .