Link Column cannot be unlinked in older CS versions.

When a dialer campaign is linked to a script, and you map call list columns to fields in your script using the Link Column attribute of the field:
To unlink the field select the blank option just under "Please Choose" on the drop down menu.
On older CS versions the blank option was not present and so there was no way to unlink a field.
Note: the above screenshot and the user guide are of the older CS version and so do not include the blank option in their screenshots.