How did sessions connect when the service was not online?

Hi, DBAs

This is a five-instance, 11.2.0.3 RAC on Linux x86-64.  I added a service name with srvctl named pager.  Since Dec 14, 2014, pager is preferred and online on instance 1, and available on instances 2 and 3.  Neither instances 4 or 5 are configured for the service.

I added a logon trigger to prevent regular users from connecting on the default service name.  I assign user profiles to enforce the trigger.  Only users like system and dbsnmp can connect using the database name; their user profiles are different than regular users. 

It worked well other databases and on this one, right up until I found four, jdbc-thin sessions from a regular user on instances 4 and 5.  The unexpected thing is that gv$session.service_name=pager, and that these were established today; gv$session.logon_time = today.