I do payroll in a call center... your stress level and pay will be directly proportional to whether or not it's an outsourced call center or a corporate one. From what you're saying, it is an outsourced. Have fun with that shit.
Usually "employment service" companies will pay your wage, then charge their client a markup which for a high volume client with fast turnover will be anywhere from 20-40%. For every dollar they want to pay you, the employment service will pay you a dollar and charge the client $1.40 or whatever.
Most businesses do this despite the high markup because they don't want to bother with hiring/firing, and carrying as many people on their comp policy. They also don't have to offer you benefits since you're not their employee.
I did payroll at an employment service before here.