While changing base channel of the client system using "rhn-channel" command, why does the command fails with error " Error Class Code: 38, The system is already subscribed to the specified channel" ?

Issue

• While adding a base channel using rhn-channel command, it fails with error :

# rhn-channel --add --channel="rhel-XXX-server-X"
Username: <username>
Password:

Error Message:
    Server already subscribed to 6949
Error Class Code: 38
Error Class Info: The system is already subscribed to the specified channel.
Explanation:
     An error has occurred while processing your request. If this problem
     persists please enter a bug report at bugzilla.redhat.com.
     If you choose to submit the bug report, please be sure to include
     details of what you were trying to do when this error occurred and
     details on how to reproduce this problem.