I have 2 Spotify usernames one that I don't really use which is connected to Facebook and then the other which is a premium account and where I have all of my playlists.
I recently got a new phone and I was trying to log onto Spotify, even when I put my username and password on the section below where it says log on via Facebook and I click the green log on button, it still logs me onto fb account.
I then thought I'd try logging off the app on my mac to see what happens and the same thing happened there. Even though my username for both is different.
I then did forgotten password and used my email connected to the premium account just in case I was putting in the wrong username. Reset the password, logged on successfully via the browser using the username I knew was right.
So I can get onto the right account using the Web player but not on any app.