How did you become aware that there was a problem 2 weeks ago if the pay cheques only arrived yesterday?
I suspect this is some Manager totally unaware of any agreement that may be in place acting off his own back. He should at the very least be informing the staff of the action well in advance as many people do rely on the quarterly payment. I would suggest you push your rep for an answer and then persuade as many as you can to join Prospect-it sounds as if the general manager is taking advantage.