Who do i talk to & are they taking advantage of me?

I do Home Care at a small agency. Since I’ve worked for this company any client that needed shower assistance, or brief changed i got paid $14 an hour which would be called “CNA case” well.. I’ve been working with a client since July.. it’s now October, & the women that does pay roll called me and said “I’ve been over paying you, you’re only suppose to be getting $13 an hour, and I’m doing YOU a favor by not telling the boss because she’ll make you pay it back” i told her, no. I wouldn’t be paying her back because that was YOUR job that YOU messed up on, not only that but for 3 months I’ve been getting paid $14 an hour and no one caught it? I find that hard to believe, & when i was told about this case it said “CNA” which means $14 an hour like any other CNA case i did. I call the boss & she knew about it as i expected.. even though the lady that does pay roll said she didn’t and she wouldn’t tell her to do me a “favor” and the boss was sitting there arguing with me about how i call out on my other clients, i asked what did that have to do with my pay now & she was just blabling on & on about nothing.. is this right? Can she do this? Nothing in this clients needs have changed.. I’ve been doing the same thing with him for 3 months now showering, changing his brief every 3 hours and putting cream on his bum.. id think of this was truly a “mistake” and i was truly only suppose to be getting paid “13” that she’d say “ I’m sorry, you’ve been working for us for 2 years I’ll keep you at that pay” this isn’t the first time they’ve messed with my pay!! Who can i talk to and does this sound right? Can she do this?