I reduced my hours at work after I returned from maternity. Flexible working request approved by HR for 3 days at that time. For a few months I took on more hours to suit me and the employer at the time but now circumstances have changed and I want to go back to 3 days, but I’ve been told this is not allowed and have no choice but to stick to the 4 days which I’ve been doing. I never signed anything or had a meeting to document my hours increasing, is this even allowed?