Short Notice Shift Changes

The bane of my life at the moment is currently short notice shift
changes. I'm a relief technician which means I have no permanent crew
mate or shift pattern. I cover for peoples absence due to sickness or
leave. This is usually fine, currently I'm working mainly weekends out
of choice to suit my wife's working pattern and keep the kids out of
child care. However sometimes the Scheduling department really do piss
me off. Normally this is when they change my shifts with less than 24
hours notice to suit the Trust. I know that operational needs mean
that I have to change shifts to fill vacancies. All I expect is to be
told rather than have to find out for myself. A simple emailwould be
nice.