Last February my mom told her assisted living facility to quit making her bed every day ($46.50/month). However, they continued to charge her every month. She did not notice this because they do not provide itemized billing (they used some kind of code). They will only remove the current month and say that the staff does not chart each day.
I suspect that this is par for the course with AL facilities. My parent was in a NH for about 5 years and we had periodic reviews of their "level" of care, and changes were made based on a monthly charge. So I suspect the facility is not just giving you a line, they do not have the ability to charge for some days and not other days.
Be prepared, when your mom dies, you will have to return that month's and the former month's Social Security check, too, because (little did anyone realize....) the Soc Sec checks are paid in advance. My spouse's parent passed away recently, in the middle of a month, and they had to give back that entire month's SS check, plus the previous month's.
So, a "monthly" charge is sort of normal. It's sad but it's true.