Sitter issues.

I went back to work when my son was 2 months old. I work 3 days a week always Tuesday and Thursday and normally Monday but sometimes it switches. My mother in less and her mother are my sitters which is awesome when they actually do but for the past month and a half or so they keep making plans on those days and going up north for the whole week and not telling me until the day I get my schedule for the week so I have no time to figure out a different sitter or people to cover my shifts.