It seems obvious that ITSP providers should be added to providers.conf file, But I can see [Trunk_1] in my users.conf file? Trunk_1 may have been created when I tried to add ITSP provider from the GUI.
Should I be changing Trunk_1 in users.conf to add provider? Or should I just forget Trunk_1 and just add the ITSP provider in providers.conf.
You may add/edit trunks from the GUI.
You may also make all the changes manually in users.conf- just copy/paste existing trunk_1 definition and change the name to trunk_2 or something more meaningful for you.