Can my employer cut my residual income form commissions if I am absent due to illness/vacation ect

I am a salaried employee who gets commission on top of a small base. Recently my employer started to deduct my residuals by the days I am absent/late ect. (I am 8 months pregnant, going on leave tomorrow....they said they wont give me any residuals while I'm on leave and some of my absences are due to DR's apts.) They say its because I am "unavailable to service my clients" which is untrue because they have access to my cell phone which I don’t get reimbursed for and most clients don’t call us anyway, they call support. I didn’t sign anything agreeing to this and it just started in January but I've been receiving residuals since June of last year. Is this legal? Can they make commission only employees have a set work schedule? Also, we are telemarketing and they currently require you to stay after hours with no over time pay to work proposals. We aren’t allowed to work them during the day & if you don’t stay they stop filtering proposals to you. Is this legal? Thanks!!