If new employees have to go through training for a new job and don't get paid, it is illegal, even for training. For commission-based salespeople, though, the definition of "getting paid" can be quite different. The real question here is what to do about it. Being new to the job, the last thing you want to do is make waves, so you should probably just let it go. You don't want to be labeled a malcontent from the get-go.
However, this doesn't bode well for your new employer that they treated you this way so soon. What next? Keep this in the back of your mind and see if you can detect a pattern. If so, it may be time to find a new job.