iPhone Air added to ABM by vendor automatically assigned MDM server even if Default Assignment is None for iPhones

You would have to ask those who have access to your ABM.

andu861 wrote:

iPhone Air added to ABM by vendor automatically assigned MDM server even if Default Assignment is None for iPhones.

There is no info about assignment in Activity report.

How can I find out what or who assigned this device to an MDM server ?

ask ABM.