Re: Oh deary dear...
Not me employing them, but the nature of hotel work in London at least means that even if you've got a loyal cadre of completely by-the-book permies, you'll still have a great deal of agency workers coming through your doors to cover for seasonal fluctuations, sickness cover, etc. As far as I'm aware these aren't vetted a great degree so the occasional bad apple is a statistical inevitability.
As another poster mentioned, use of WhatsApp is universal for notifying people of their shifts as well as other day-to-day business and there's no exfiltration protection or endpoint security at all.