I am due to go back to work in 2 weeks after a year on maternity. I was previously working 40 hours per week Monday to Friday. But will be reducing to 16 hours - 2 days a week which are the days I have fixed child care. This was all agreed with my manager 6 months ago (a lot earlier than it need to be done by but I wanted to know it was sorted). I have it all agreed in writing and the acceptance from HR who have also agreed to the new hours.
However, since this has all been agreed two people have handed there notice in and left, leaving staff shortages on certain days of the week. I'm now being made to feel guilty about working the 2 days I've already agreed and have been told I may have to change the days. This isn't doable as I won't have child care for the days they are now wanting me to work so would mean I will have to hand my notice in and be left jobless.
Can the company legally change my new hours after already agreeing to them?