Conference / meet-me transfer trouble

I am running TB 2.2 with asterisk 1.2.24 plus A2Billing 1.3.0.

I have watched the Conference tutorial and added a conference in freePBX and don't seem to get it to work.

I have spent some hours googling, but haven't found actually a clear-cut user-procedure.

In contrary to the tutorial, I want to call-up the persons myself and then transfer them into the conference room.

So, I called an external person, he picked up the phone, I pressed [Transfer] 2000 (my configured conference room nbr) and then the called person hears "Please enter your complete pin number" which is a A2Billing prompt.

The best would be, if I could setup a so-called dynamic conference but I am not sure which of the scripts I found would actually work.
(One I found, is at http://www.voip-info.org/wiki/view/Aste ... ces+macro)

Is anyone - using a config for dynamic conference, which works with my above listed components and versions?

Or, in general, has anyone a static conference with the above specs working with the possibility to add called persons into the conference room, using SMOM 300 phones?

I really, really appreciate any help!

regards, devplan