To paraphrase Austin Powers, there are only two things I dislike in this world: nuclear war and shady-ass shops. Unfortunately, the latter abounds throughout the world, and especially in the United States. And they can be everything from small mom and pops to those run by large, corporate dealerships. The problem is you just don't know who's the good eggs versus the ones that'll rip you off.
You just have to roll the dice, but you're rolling said 20-sided die with what could amount to thousands upon thousands in repairs, or not having your vehicle fixed in a timely manner. Add how complicated manufacturers have made modern vehicles so complicated you likely need an advanced degree just to figure out how to replace your vehicle's brakes, and you get a system that's basically designed to screw the consumer over.
But none of that excuses these shops for their behavior.