I brought the car in to fix a horrible grinding noise in the engine. After a $80 'diagnosis', they told me I needed a new water pump.
Halfway through the repair, they called on the phone, told me that the noise was fixed but that they had noticed I needed a new power steering pump.
I declined that repair, and when I picked up the car (and paid $900 for a new water pump), it turns out the noise was not fixed, it was the power steering pump all along. They LIED when they said the original noise was fixed, hoping I'd authorized the other repair and that I'd never find out that there was never anything wrong with the water pump.