I have been told on numberous occasions that when I setup a 3 party conference call, that neither party can hear each other. The volume is very very low for them. As the person that has setup the conference call, they can however hear me just fine.
I have MeetMe conferencing enabled but I am just using the 3 way conferencing in this case.
When I establish a meet-me conferencing bridge, the volumes for all the parties are fine.