Poor service delivery from Engin garage

So my wife took her car to an engin filling station in our town and luckily she did not fill up the car this was on a Thursday. Later that day the car started behaving badly where it would cut out and loose power. Monday morning i made an appointment with my local Toyota dealer to have a look. The technician adviced us to fill up the car with diesel from a different station to see of its the diesel causing the car to act funny and so we did. Strangely enough the car was perfect and in running condition. I placed a post on facebook warning people not to fill their cars with diesel at this garage as we had problems strait afterward. So the manager phoned me from the station letting it all out and how its our mistake as we should have spoken to him after all this. Lots more people started commenting and complaing about service delivery and just how bad their experience was with this garage. And according to numerous people that have reported to the manager but nothing gets done regarding the problems so why would i then waste my time with someone who just dont care? Long story short he threatened me with lawyers and the popi act for shaming his business. Well in my eyes i think is tood up for everyone who was just affraid to say something. But now i can see why a lots of people are complaing cause according to him all who is compaining is incorrect and he even said that i properly support different gas station's and i am just trying to make him loose business. Well sorry for him but i am not in the fuel industry. So good luck with the next comeback.