Hello there!
You can enable the ONLY service for the subscriber A and then register the service.
By default, a user has the ONLY service rights and does not need to be configured. The ONLY service can be registered in any of the following modes:
- The administrator registers the service in the USM web management system.
- A user registers the service on the BMU self-service portal.
- A secondary number user dials the ONLY service access number *85*TN# on a phone to bind to the primary number. Here, TN indicates the primary number of the ONLY service.