Hi,
You can opt following options after deleting AD synch.
Clients will reappear in the default group as they check in, unless you enable automatic creation of client groups by editing "scm.agent.groupcreation=true" to the conf.properties file
Add "scm.agent.groupcreation=true" line at the bottom of conf.properties
Conf.properties file will be available under C:\Program Files\Symantec\Symantec Endpoint Protection Manager\tomcat\etc
In this way group should automatically created under My company & clients should connect to their respected group.
let me know if it worked.