Incompetence - negligence - no after sale service

I took my vehicle to Greenstone Gearbox and Dif ..specialists on the 10 November 2015..with slight gearbox problem in one gear..I was told they had to recondition my vehicles gearbox...I gave them the go ahead and R 16200 later I collected my car on the 13th November and paid in full....a few days later things started going wrong with my vehicle . Firstly my overheating light kept alluminating, I took it to a radiator specialist , they tested my cooling system . was told it was functioning perfectly...then I experienced major loss of power.,.took it to agents they replaced spark plugs..with no success...then took my veicle to AMS in Edenvale ,.they at last diagnosed the problem to the reverse gear counter weight incorrectly fitted when gear box was replaced causing a direct short with the started motor...took it back to greenstone , they refused to except responsibility....today heard knocking noise on my exhaust took the vehicle to Tyres and more edenvale .. was told the bracket holding exhaust to gear box in incorrect position the pins through the bracket would keep pulling out as gear box had been refitted incorrectly....I will be suing for complete new management system