As Kim said you can't turn services on/off for an OrgUnit with GAM. However, if you create Google Groups for each service, you can enable the service for that group of users and thus use group membership which GAM can control to enable/disable this service.
It'll take some work and planning to move from OrgUnit-based service enablement to group based. I'd recommend provisioning all the correct groups and memberships, enabling their respective service for them and only once that's been in place for 48 hours turn the services off for your OrgUnits.
Jay