Merging Calls

I have a few issues/questons on this, we are able to call a participant and then add a 2nd call but are not able to;

1. Add a 3rd just rings busy, if I am reading the manual correctly it says the phone can add 5 participants (Trio 8800). I am thinking since I can't merge this may be the issue, see point 2.
2. Merge the callers, I see in the user manual this must be enabled but I can't find how to do this in the admin manual or through the interface. "If your system administrator enables the conference management feature, you can mute and remove
   participants from the conference". When I get 2 calls going, one is on hold and the other is active. the menu doesn't have the Merge option stated in the manual.

I am a bit confused on this as this is a Conferencing phone, this should not be this complicated? Any suggestions will be appreciated.