Calisto P240-M: Can't Stream Music Without Hearing Dialtone

Why can't I stream music without hearing dial tone?

Lync provides a dial tone whenever the device is off the hook. You can change this setting through the Plantronics Control Panel:

If you do not have Plantronics software installed, do so here.
Once you have downloaded the Plantronics software, go to Start > All Programs > Plantronics > Plantronics Control Panel.
Click the Preferences tab.
Clear the Microsoft OC/Lync Dial Tone Enabled check box.
Click OK.