I have purposely tanked my Sunday shifts

Essentially, I was working all day on Sundays. This was never in my official contract, technically I shouldn't have been doing it. Weirdly enough tho, HR officially recognised this unofficial contract. Anyways, based on the events of 2 Sundays ago, I've decided to tell HR that I won't be doing all day anymore. The results have been glorious.

I was the first person in the fitting rooms at 10:30 this last sunday instead of 09:30. There should have been someone in the fitting rooms to help open at 10:00. There wasn't, despite being on the rota lol. Another person was due to come in on returns at 10:30. He also wasn't in. The fitting rooms were an absolute shit show, the guys closing last night were both new and both unsupervised. And no one was there to help as I had to jump straight into serving customers.

The people from the replen team, who are meant to be putting new stuff out, were instead in the fitting rooms trying to process and complete the returns. On top of that they were having to man the fitting rooms which they're not too experienced with. There was a big queue of people when I started, I'm assuming they were there because no one (me) was there early enough to open lmao.

Obviously this had a knock-on effect, and not all the new stock could go out in the morning. And I wasn't there to close the fitting rooms, not entirely sure how that one ended.

In another 2 blows to the fitting rooms, we had summer hours which have now ended. One of my mates was closing the fitting rooms every Sunday, now he's back on his original contract which is Saturday's only. Additionally, someone from the returns team has quit recently. She was great at returns and had to cover the fitting rooms for someone who left a couple months ago.

TLDR; I've dropped my unofficial contract and am currently watching my department shatter into pieces. Temporary contracts ending plus 1 person quitting is adding a lot of fuel into the fire. Especially as we were understaffed before this person quit.