Is there a Conference Call feature on ATT MLS 12D?
If by conference you mean inside and outside parties connected together the answer is yes. You should have a CONF button on the set. You press CONF, dial your second call and press CONF again. You can press CONF again and do it all over again to add a 4th party. There are restrictions and the conference is not amplified. Here’s a User guide to Partner phones. pdf page 3 has CONFERENCE instructions. http://public.carl.airpost.net/Avaya/Partner%20Phone%20User%20Guide.