Which dial plan function restricts calls that are made by a lobby phone to internal extensions only?

Manipulation of dialed destination involves digit modification (e.g., adding a prefix), not defining what numbers can be called at all.

Path selection determines the optimal route for a call after it has been authorized, not the authorization itself.

Calling privileges, implemented through partitions and Calling Search Spaces (CSS) in Cisco UCM, allow an administrator to define which destinations a particular phone or user is permitted to call. By assigning a lobby phone to a CSS that only contains partitions with internal extensions, outbound and external calls can be effectively restricted.

Endpoint addressing refers to how devices are uniquely identified within the system (e.g., directory number), not their calling restrictions.