Supply of unserviceable second hand diesel engine

My complaint is in regards to: "USA Spares" or "Jeep Spares" 521 Bosch St, Hermanstad, Pretoria, 0082 Tel: ********** ********** The mechanic who was repairing my car purchased a 2.5L diesel engine from USA spares. The first engine (invoice 506862) they supp**** was the wrong engine. The second engine (invoice 139377) they supp**** had an oil problem (no oil pressure) from the first time it was started. After some delays, they eventually agreed to send a flat bed to collect the car for them to have the engine repaired. More than a week later they said that it was ready for collection. On the first test drive it seemed OK but then the oil problem returned. When I called them about this, a "Jannie" from USA spares said that I should take it to the mechanic to have the diagnostic tester analyze the problem. The diagnostic tested did not report any problem. When I was on my way to them from JHB, so that they I could try to convince them to have it repaired, the engine failed completely (mechanically broke) so I had to have the car towed back to the mechanic in JHB as he was nearer. USA Spares (Charl Labuschane) are now refusing to assist me as they say that the 30 day warranty period has expired (which had already expired by the time they first collected the car). It was within the 30 day warranty period that the original oil problem was reported to them and it was never correctly fixed. The 30 days has only expired because they deliberately delayed the repair. The engine that they supp**** was never really fit for purpose even after they supposedly fixed it, it still had the original oil problem, which I suspect led to the catastrophic failure of the engine. They have been delaying giving me an answer for almost a month now, and only when I pressed them for a decision did they actually admit that they were not going to do anything. The people that I have been dealing with are: Aubrey (no surname), he only once returned my many phone calls. Charl Labuschane, he claims to be the manager, but never returned any of my calls.