I spent a little while yesterday looking at an issue where a DDI number was not working on a FreePBX box. Now, I’ve set up a few trunks and inbound routes over the years so don’t normally struggle too much! but this was down to a bug (in PHP I think).
Under certain conditions the Asterisk dial plan is not written out correctly by FreePBX, causing incoming calls to fail.
Check out this post for more info – http://michigantelephone.wordpress.com/2012/04/25/php-bug-can-cause-f-pbx-inbound-routes-and-asterisk-phonebook-entries-to-not-work-as-expected/