A system can only be registered with one subscription service. If you need to change which service your system is registered with or need to delete the registration in general, then the method to unregister depends on which type of subscription service the system was originally registered with.
38.1. Systems Registered with Red Hat Subscription Management
Several different subscription services use the same, certificate-based framework to identify systems, installed products, and attached subscriptions. These services are Customer Portal Subscription Management (hosted), Subscription Asset Manager (on-premise subscription service), and CloudForms System Engine (on-premise subscription and content delivery services). These are all part of Red Hat Subscription Management.
For all services within Red Hat Subscription Management, the systems are managed with the Red Hat Subscription Manager client tools.
To unregister a system registered with a Red Hat Subscription Management server, use the
[root@server ~]# subscription-manager unregister --username=name
This command must be run as root.