I logged onto google music on a friend's android to try to subscribe to Google Music family plan for my iphone. Now I can't log out of my account on his phone. Any suggestions? Thanks
Go to Settings> Applications> Apllication Manager> Google Paly Music> Storage> Clear Data
Now you will be logged out of any accounts in play music.
Important Note: Next time when you open Google Play Music, do turn of your internet connection or else it will automatically log you in with default account set up on your device.