The solution depends what device platforms/modes (OEM specific Android+,  Android Enterprise Device-Owner mode , or Android Enterprise Work-Profile mode).  

Could you please check what are the active MDM API's reported in the configuration tab of your device agent?

Also, what are the version and builld numbers of your MobiControl server?

Hello Darius,

Thank you for your post, please use Application Run Control profile where you can blacklist unwanted websites and applications of the device.

Please refer the below link - 

https://www.soti.net/mc/help/v15.0/en/console/reference/dialogs/profiles/androidplus/profile_appruncontrol_androidplus.html

Regards,

Merely using application-run-control to disallow Google Play app may have a number of drawbacks, but is likely the option for any device using OEM specific Android+ device agent.   Please note that some earlier MobiControl server versions do not have application-run-control profile configuration payload for some device platforms/modes

However, if your device is enrolled into Android-Enterprise device-owner mode, there is feature-control option to disallow device end-users from adding any Google account, while the managed Google play account from your MDM server ensure that allowed apps on the device can still get updated/installed from Google Play store.