Work not paying. Is it legal?

I have a problem with the comapny I work for. They have always had a little bit of a reputation with not following laws exactly. They are very stingy when it comes to paying employees. We only get payed for the time a customer is billed; we miss out on .5 to 1 hrs often usually a couple times a week. I just had an incident where I took attended a day full of cles which are NEEDED to progress at work and recieve a salary increase. After 7 hrs of sitting in the office doing these cles I learn I am not going to be paid for it. Is this legal? Where can I go for more information on this topic?