Delete an external device management service in Apple Business Manager
You can delete an external device management service, and reassign or unassign devices that have current assignments with it.
Important: If an external device management service with current device assignments goes offline instead of being deleted (for example, due to a network issue), the devices continue to use the last known management configuration until you assign them to a new service, or you erase and reactivate them.
Delete an external device management service
In Apple Business Manager
, sign in with a user who has the role of Administrator or Device Enrollment Manager.Select your name at the bottom of the sidebar, select Preferences
, then select your device management service 
under the Your Device Management Services list.Select the Delete button
, then do one of the following:Select the service you want to reassign the devices to, then select Reassign & Delete.
Select None from the services list, then select Unassign & Delete.