I'm using SQL Server 2014 Enterprise edition.
I have created an alwaysOn Availability group on a named instance and configured a listener to it.
When I try to access the listener from SQL Server Management Studio it logs to the default instance. I configured Endpoint URL to point to the named instance and gave a static port to the instance too
Also note that I have configured endpoints to listen to the same port in both instances.
I have no idea why that is.