Unwanted user accounts appearing in Apple Business Manager

All the devices within ABM now have two new users, myself and my manager. We're both managers / admins of the AMB - but we don't need personal accounts on all the machines, that's not how we work. How can I get rid of all of them safely and stop from appearing again?

Cheers,

Adam

[Re-Titled by Moderator]

Original Title: A user with my name has appeared on all the Macs in my apple business manager account.