Try putting the mic into the charging base. This will disable the mic and allow you to delete it from the remote.
To delete the Calisto mic from the remote:
1) Enter Menu.
2) Scroll to Initial Setup (press on “up” arrow to jump to bottom of list),
3) Scroll to Headset/Base (press on “up” arrow to jump to bottom of list), then select.
4) Select Pair New Headset.
5) Select Remove Headset.
6) Select Delete to remove previous headset.
7) Select Pair Headset to pair new headset.
Put new headset into pairing mode and go from there!
NOTE: This may also work with other bluetooth headsets that cannot be deleted from their phones. Try plugging them into a charging adapter, then delete them.