Open Settings > Lists.
Find the list and check its source.
Under Assigned to, choose the responsible sales rep.
Click Save.

The list then appears on their calling page and its results count toward their activity. An unassigned list can be configured by an administrator, but nobody can start it.
Reassign the lists of someone leaving the team before removing their access. If the new owner does not have the same calling number, Ubic selects one of their numbers when possible.