How much does a CNA get paid?

Hello everyone,

I wonder how much a new CNA get paid in Phoenix metropolitan area? ( in LTF or Rehab.)
I will work night shifts on weekends.
HR staff from my employer suggested $11 for 1 or 2 shift on weekdays.
Then she told me that she will pay $12 if I will work on weekends.
I wonder if I will work night shift on weekends and I can get paid more than $12.

Another question is that when I can ask my agency to raise my pay rate if I work with agency.
Does agency pay with same rate, even I work night shift on weekends?

Thanks in advance.