err, just one extension and configure it via service center?
so, in the operation-tab of the extension you have a "Logical Database" information
there you point it towards the correct database.
this you will change according to which database you have to point to.
those database-connection are set in the adminstration tab and then databaseconnections.
see for more info: http://www.outsystems.com/help/servicestudio/9.1/#t=Integrating_with_other_systems%2FConnect_to_an_External_Database.htm
how do you name the entities?
Chances are you have the "table or view name" as something like "somename"."myentity".
and you simply have to remove "somename".
furthermore, are you sure that logging in via the new connection you do get the new schema?
if this is not helping, I suggest to provide some example and "dummy" screenshots of the several connections etc...