If agents are online you can make internal calls to them. All you need to do is click the agent name under the Team list and click Call.

Agents who use Simultaneous Ring will also only receive the call on her/his computer, not on the phone. This is because internal calls are not forwarded to external numbers.

Please note that if an agent is on an existing inbound/outbound call, then you will not be able to make an internal call until their line is free.