You can control which Agents have access to Voice by going to Agents > Agent Profiles, selecting the Agent and setting their Voice permissions there.

Deleting Voice Recordings and Messages from Tickets

Please note to grant Agents the ability to permanently delete Voice recordings and messages from Tickets. The relevant permissions can be found in Agent > Agent Profiles> Permissions > Tickets. You can set whether Agents can delete Voice recordings and messages on their own, team's, followed, unassigned or others' tickets.