Aastra 6757i CT User Manual page 137

Expansion Module Keys
6. Select from "Key 1" through "Key 36" (M670i)
or
Select from "Key 1" through "Key 60" (M675i)
7. In the "Type" field, select Services.
8. (M675i) In the "Label" field, enter a label to apply to this key.
9. Click Save Settings.
130 Model 6757i CT IP Phone User Guide