When I take my car in to be serviced, if the hourly rate has risen, even though I am a steady customer, I pay the new rates. The catch with providers is that once we know the fee, we tend to put it in the envelope each time without rechecking the rates. This caught me once, and I abjectly apologized. She said, never mind, I knew what happened, but I only want to stiff a lady in a fun way. Several years ago, when many ladies lowered their fees, I heard not much griping.
The short answer, is the lady can do darn well what she pleases about charging. We just pay and lay.