All users with access to the dialer can call another number in an ongoing call.
Have you ever tried to get in touch with the wrong department or person, where they kindly give you the correct phone number. Then what do you do? It is possible to call another phone number without closing the lead you currently have open.
First, you need to create an additional phone field available on the campaign.
When talking to a lead and they give you the correct phone number to call, input the phone number in the extra phone field.
When you have input the new number, hang up on the current call.
Now, copy the number from the field, paste into the dialer and press the green button to call.