It’s possible to make a multiparty audio conference between max 4 persons.
To activate it during an active call, you can add a new person tapping on the “Add Call” button.
During this fase the other party will be placed in hold.
After the second person answered you can tap on the “Conference” Button to have both parties talking with you.
You can repeat the adding call process one time more to be in 4 people talking the same time (you + others 3 ).