I work at an auto dealership and sell parts all day to local business's, body shops etc. I currently have a Avaya Definity 6416D+ in the back of the phone there is an option for a headset. What would I need to make this work, I have been goggling around and it seems I need a headset and a cable/cord to plug into the back of the phone. I cannot really get a feel for what I would need and don't want to order a bunch of wrong stuff. Is there anyone who could point me in the right direction as to what I would need to get this going?