Uh 7-11’s name came from the fact it was open from 7am to 11pm originally, so being open 24 hr/day is not an inherent promise of the brand.
That is straight from the FAQ on their franchise site, so they do think it is part of the brand - despite the history of their name, which I'll admit I didn't know - and thank you for the TIL moment.
We, here at our office desks, are quick to demand that this store or that service is open 24/7.
The guy needed a day off. Go somewhere else and get your chocolate bar.
If he wants a day off then he should take a day off - I don't think 7-11 is setting his working hours or vacation days, but they do expect him to manage his store the way he's agreed to.