Inside the contact card an agent can view the history and comments of that specific card. This tab can be reviewed regardless of a call being made and cannot be hidden from the agent's interface.
Entries into this table can only be made after a call has been done, as the comment is directly linked to the phone call's entry.
The agent can review the comments, orders and recordings from all previous calls.
As an admin, you can set some privacy settings here, where you can block an agent from listening to another agent's phone call's recording.
This can be done from the Admin > Campaign > Campaign specific settings > Recording settings > "Agents can listen to other agents' call recordings".