Stop feeling guilty. This is the managers’ TIFU. One, they failed to ensure everyone had their phone number when they decided for themselves that they weren’t gonna use an app they knew employees used for workplace communications. Two, they FU’d when they decided not to use said app. Three, they thought emailing teenagers was gonna work and got all mad when it didn’t.

And finally, if you’re sick, don’t go in. Regardless of any circumstances management wants to whine about. Every boss is gonna resort to every legal and illegal way they can use to try to trick employees into accepting being treated like shit. So don’t give this jerk any ammo by accepting blame that isn’t yours.

Your apology to then just enabled them more.