6 Months and 55K later still not repaired

So after paying over 50K and 5 months I wanted to collect my vehicle from Megatronics SA and was threatened that if I want to take my vehicle they will drop my gearbox and keep 35% of my money paid for labour and parts but I still haven't even had the use of my vehicle they told me that the vehicle is 90% completed I then agreed to give them another 2 weeks in wich I want my vehicle 2 weeks have now passed and still excuses that the vehicle is still not completed I'm fed up 6 months now and still not getting anywhere with them they have my vehicle my car got damages my battery has been removed by them and replaced with a smaller battery and when we get frustrated and start swearing at them we get told not to threaten them as they will remove the gearbox and keep 35% of our money already paid to them so it's my car and 55K down the drain and they are happy and we as clients just get nowhere we have another vehicle that's going to loose it's motor plan because of Megatronics SA as it's the only transport we have at the moment and cannot send it in as we will then be left without transport it's pathetic that a customer must pay 55K and still not have the vehicle for 6 months and Megatronics SA just gets away with it