The trouble is, thats not strictly true. If you put your car in for work, and worn/broken parts fail due to dissasembly and the garage "find" another fault, it is down to you. regardless if the car was driving ok before or not. If you are in doubt that the parts were faulty before dissasembly, you need to get them inspected by a neutral
PROFESSIONAL (important that bit
) body who can possibly confirm your suspicion's, and who is prepared to put their findings on paper for you. Then you can argue your case, otherwise its your car, your problem. And if you sign a bit of paper agreeing to the work, the garage can withhold the vehicle if you change your mind and decide you don't want to pay.
Sorry