Don’t recognize trusted phone number

I work for a school and unfortunately as is the nature of business we let a lot of staff go- and we have three iPads that have a work email address, which I know the password for but the trusted phone number is not familiar— after looking through our databases. Now, I can’t access that AppleID, because I’m locked out and I can’t sign out of those iPads which are logged in with that locked AppleID; because I would need to verify on the trusted device. Any thoughts? I can’t even “erase all data and settings” on the iPads.