To do a conference call on a Cisco SPA501G phone, from the Cisco SPA501G dial the first number you want to have a conference call with. When they answer, press Conf (the soft button that appears on the screen), then dial the other number you want to have a conference call with (press dial after entering the number). Then press Conf to take the first person off hold and enter the 3 way conference call.
❗ Note: You may have to press Conf again if the first person doesn’t com off hold.