FreeSwitch conference with external callers?

Question

Asterisk

Hello. Interested in organizing a conference of local sip clients, for example, with phones of mobile operators or fixed phones of other organizations. Everything is clear with local ones, a group is created in /etc/freeswitch/directory/default.xml

<group name="support">
  <users>
    <user id="007" type="pointer"/>
    <user id="017" type="pointer"/>
    <user id="082" type="pointer"/>
    <user id="218" type="pointer"/>
  </users>
</group>

further on a call to a certain number, the users specified in the desired group call and rush into the room

<extension name="main_conference">
      <condition field="destination_number" expression="^3000$">
  <action application="set" data="conference_auto_outcall_caller_id_name=Conference"/>
  <action application="set" data="conference_auto_outcall_caller_id_number=1"/>
  <action application="set" data="conference_auto_outcall_timeout=60"/>
  <action application="conference_set_auto_outcall" data="${group_call([email protected]${domain_name})}"/>
  <action application="conference" data="[email protected]+flags{endconf}"/>
      </condition>
    </extension>

and how to call a number that is not in the friswitch and, accordingly, it cannot be specified in the group. For example 8922ххххххх?
I’m just getting acquainted with the Friswitch, and here is an urgent task from the boss ((
I read this article, it says that you can transfer any called subscriber right during the conference, if I understood correctly. But I didn’t manage to do this.