My pay is being withheld to pay someone else’s taxes

I recently started working as a temporary cleaner. I work under a cleaner that is officially employed there, but I was hired as a service. This is not the only place I clean and I am self employed. I was told I would be paid $200 a week and I would be paid monthly. After three weeks, I found out that I am actually getting paid half of the other cleaners paycheck after tax is withheld, as in they get their paycheck, and then pay me under the table. This would only be $160 a week. I feel like I'm getting screwed because I would likely get most of those withholdings back in my tax return, but as they're technically from someone else's check, I wont. I'm shocked and I dont know what to do here. I already did almost a month of work.