All users with access to the dialer can transfer to an external phone number.
Before agents can transfer a call to an external phone number, it is required to enable call transfers from the campaign settings. See how to do that right here.
When an agent is in an active call, there is a transfer option right next to the call/hangup button.
When you have clicked, a transfer box appears. Enter the external phone number in the field at the top.
When you have input the phone number, you have two transfer options at your disposal.
Transfers the call immediately without talking to the recipient beforehand.
Makes it possible to speak with the recipient before sending the call through.