In order to get the headset button to work, we may need to activate it 1st.
1. Hit the feature button (Infinity symbol or a circle with an X in it)
2. Dial 315 to activate headset mode (deactivates speaker)
MUST USE SPEAKERPHONE BUTTON TO ANSWER/END CALLS.
DIAL 316 TO ENABLE SPEAKERPHONE AND DEACTIVATE HEADSET MODE.
(Some Mitel phones use 317 as the code to both activate and deactivate headset mode)