Oliver,
to call inbound, your going to have to have freeswitch listen on external interface as a first start. The setup is different depending on .81 or .90 beta version.
Its possible with some ISTP's to route inbound DIDs directly by IP address only. This is the preferred way since no way a hacker can originate calls back thru your provider and ring up toll charges. In this case there is no need to setup a gateway like below (which basically has freeswitch register your itsp switch)
However with GATEWAY , if everything is setup correct, after you add gateway and reboot, you should see some messages in fs_cli that you successfully registered. There are some fs_cli commands to list the active gateways etc... the freeswitch wiki details these.
So dial the DID number from your phone, and watch the fs_cli console realtime, and you should see the call hit the dialplan.... albeit it will not answer quite yet. But this needs to happen before proceeding to next step.
The last step is modifying the dialplan so a call that come in is routed to the right BBB voice bridge.
You can prompt them for vbridge and route dynamically, or just hardcode a caller-id-number to always bridge to one particular conference.
Anytime you make a change to .xml you need to restart freeswitch, or just run reloadxml in fs_cli
regards,
Stephen