When The Listener Status is showing like the below :

Services Summary...
PLSExtProc has 1 service handler(s)
insA has 1 service handler(s)
insA has 1 service handler(s)
insB has 1 service handler(s)
insB has 1 service handler(s)
The command completed successfully

Its working like the below from the client


SQL> connect system/manager1@insA
Connected.
SQL> connect system/manager2@insB
ERROR:
ORA-01017: invalid username/password; logon denied


Warning: You are no longer connected to ORACLE.
SQL> connect system/manager1@insB
Connected
- But connecting to insA
or saying this also invalid password

If the Listener is showing only one service for each instance then its working fine