The service of BMC Workshop is terrible

I took my car to BMC Workshop at 69 Watkey Street, Orangesig, Bloemfontein 9301 and the service that I got was unpleasant at all. I waited almost two months to get my car from that workshop. The problem that I had with my car was a gear box and I spoke to the owner of the workshop by the name of Frans what he said to me was that for me he could get me a gear box from Cape Town and that gear box cost R15, 000 and his labor is R4, 000 and courier is R2, 000 all in all I paid him R21, 000 thousand to get my car fixed but still my car it's not okay. Last month when I went to fetch my car I asked him invoices of were he bought the gear box and courier he couldn't give me them and he said to me I must come the next day for the invoices. I went to him and he said to me that he forgot and he will call me once he got them, still to date he never called me. And I also said that I want my old gear box back to my surprise he said to me that the gear box was a trade in. So I felt like he only repaired my old gear box and there was no box that he bought from Cape Town and if there was a gear box that was bought from Cape Town all I need is those invoices because I believe they are mine since I am the person who bought that gear box even the courier one cause I am the one who paid for it. I am not happy at all with the service of BMC Workshop it clearly shows that they are used to chow other people's money. All I want is my invoices if there are any no invoices I want my money back that's all that I am requesting from him. And his numbers are as follows 060 672 3117