Hi @Erika Nevins ,
Thank you for posting question to Microsoft Q&A.
According to your question, you might need to contact your old department you used to work with to delete your MFA settings from it.
Additionally, you could also uninstall Microsoft Authenticator and reinstall it again from App Store (iOS)/Play Store (Android) - this will remove all accounts from the list (even it could not be deleted). But this step requires you to set up backup MFA method for the other accounts if you have more than one account - you will need to make sure that for other account you could still access it by adding/using other verification method like SMS/phone.
Initially, please visit https://mysignins.microsoft.com/security-info and sign-in with other accounts' credential first and you need to make sure that you will not be locked out because of MFA (as Microsoft Authenticator re-installation would break the MFA verification process on current existing account) by adding other alternative verification methods like phone calling/SMS.
Caution: Please double-check if you could still sign in to other accounts with alternative verification methods before proceeding to uninstall Microsoft Authenticator.
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