dyno tech cant repair customers cars

I took my car to dyno tech for non start. And my car was kept at their premises for three months without any work done on the vehicle. After months of battling with the dyno tech team I was told that the cylinder head needs to be removed and it will cost me R3500 then I gave a go ahead. Then it took them another month to assemble the car even after assembling the car didn't start. On the day when they were closing for festive I was called and told that my car is ready I should come and collect it before 12oclock and the price suddenly was double they wanted R7500,00 and if I don't collect it they going to charge storage. Then I quickly sent someone to go and collect the car because I was out of town. When I came back tried to start the car it starts but it doesn't rev up. Now when I took it back to them they want me to pay another amount for diagnostic and they claim that the car was revving.