Piece work / Performance based pay

[baskln]

Ok this might seem kind of long and stretched out but here goes. I am a technician for a (blood thirsty) company that installs Dish Network Satellite systems. We are payed on a piece work system so for instance, If I complete a 2 room installation I receive 41 dollars for the 1 room installation and an addition 10 dollars for the 2nd room. Now my question is this. This company has recently put in place what they call a performance based pay system. It works like this: we must complete 85% of our NEW installations and have less than 5% of our customers call into Dish network and build a service call within 12 days of being at their house. These things are not TOTALLY withing our control. Reason for losing a new installation could be anywhere from there are too many trees on the plot of land to receive a signal, to a customer not home for their appointment, to safety issues such as snowy roof. The 12 days calling thing is the same. If a customer calls in for a simple issue that could be resolved over the phone but the phone technician builds a trouble call, our pay is affected. I currently make 41 dollars for a 1 room installion. With this "performance based pay" system I am going to be knocked down to 32 dollars per installation due to too many customers calling in within 12 days. I've been with this company for 2 years now and am receiving that big of a pay cut. The cut will last for 8 weeks IF my percentages get better. Can the company legally do this to us? Cut our pay based on things we don't have total control over? Please help!! I love my job but this company is going too far!