Not too sure about that -- this would prevent phone reps from ending calls when the connection with the customer isn't functioning properly (but yet the line is still active).
If true, you could pretty easily take down a call center simply by calling up and leaving the lines open with no caller. Managers would need to be running all over the place.
Since call center employees commonly have the ability to perform call transfers, I can only imagine they have the ability to hang up on calls. Otherwise, I imagine they could simply transfer the call to an invalid extension to "hangup".
