To change device ownership:
- In the Microsoft Intune admin center, choose Devices > All devices.
- Select a device.
- Choose Properties.
- Specify Device ownership as Personal or Corporate.
When a device's ownership type is changed from Corporate to Personal, Intune deletes all app information previously collected from that device within seven days. If applicable, Intune will also delete the phone number on record.
Ref:
https://learn.microsoft.com/en-us/mem/intune/enrollment/corporate-identifiers-add