Injector warranty

On the 1st of November I had issues with my 6 month old quantum 2.5D it had rumbling noises in the engine and was later diagnosed as an injector problem. 7 days later the car was returned sorted under warranty covered by Toyota Sa . I expressed concern to my service advisor at the time and was reassured that the vehicle was in 100% condition. On the 2nd of January the car started doing the same thing, so I advised the driver to take it back to the same dealer, this time they are refusing to make it right it has been sitting there for 3 weeks to date and I don’t really have valid reasoning as to why The car gave no warning on the cluster for contamination in the diesel filter. I’m doubtful that they even changed the injectors to begin with