Set the headset as the default device on Polycom IP phones
In the default settings, new calls made from the Polycom IP phone with the handset on hook are diverted to the speakerphone. To set the headset connected to the phone as the default device, enter the web administration of the phone, Preferences menu – Other preferences – User Preferences – Automatic detection of headset mode – ACTIVE
After saving the configuration (no reboot required), make the first call in headset mode by pressing the “headset” button. Subsequent calls will always use the headset unless you manually switch modes (speakerphone or handset).