Steal Extension in Use
The extension number that you are trying to use is currently in use by another user.
First check that you have entered the extension no. for the phone ON YOUR DESK.
If the extension no. is correct then check if the indicated user is still logged in?
If they are still logged, in the have a chat with them about what why they might be using your extension no.
If they are no longer logged in then they may have walked away from their desk without logging out. In this case you can ask your Team Leader to log them out.
For your Team Leader to log a user out, go to:
Account | Sessions
Find the above user's session and click the 'Log Off' button.
You should now be able to login with your extension.