I had been using a temp agency per hour with mom. I 'm transitioning to 24/7 coverage with a different group of people. I contacted the old company that i only needed them for 2 and not 3 days now.
They called the aid currently with my mom who promptly told my mom she's quitting after today because she doesn't' want to work 2 days for her now.
So no notice and my mom , not myself was notified with no notice.
On the other hand, I think some caregivers do want a minimum number of days of regular work, even via agency. So maybe that is a factor for you?
There are a lot of flaky people that work in this industry.
Just push forward.