Your Mitel office phone will save the handset or headset volume if set to level 1 through level 9. To protect your hearing you cannot set the highest level 10 - this is by design and cannot be changed.
To set and save the volume of your handset or headset:
1. Pick up the handset or headset
2. When you hear the dial tone adjust to level 1 through level 9 via the volume keys at the top right of your phone