Planning ignores unavailable dates for scheduled users.

Planning seems to ignore unavailable dates for users that are already scheduled for that date:
If a user adds an unavailable date after they have been scheduled for that date, the system doesn't warn them they have been scheduled, nor does it change their availability on the Services view to 'unavailable'. And if I change the user's availability to 'Accept' in the service view, it doesn't warn me they are unavailable. I would class this as a bug