To initiate 3-way calling
1. While on the first call, dial the 10-digit number of the second person.
2. Press the Call button. The first person is automatically put on hold while the call is made.
3. When the second person answers, press the Call button to create a 3-Way Call.
4. If the second person doesn't answer, press the Call button twice to end the connection and go back to the first person.
5. To end both conversations completely, hang up. source