Вот что показывает в логах после этого:
May 6 14:41:35 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995555914903' rejected because extension not found in context 'public-direct-dial'.
May 6 14:41:46 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995557657144' rejected because extension not found in context 'public-direct-dial'.
May 6 14:41:51 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995555760553' rejected because extension not found in context 'public-direct-dial'.
May 6 14:41:55 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995555260246' rejected because extension not found in context 'public-direct-dial'.
May 6 14:41:59 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995555783915' rejected because extension not found in context 'public-direct-dial'.
May 6 14:42:02 asterisk[1763]: NOTICE[1788]: chan_sip.c:23698 in handle_request_invite: Call from '' (5.231.192.3:5061) to extension '995571037377' rejected because extension not found in context 'public-direct-dial'.
5.231.192.3 - этот айпи довереный и прописан как host, у рабочего провайдера указан шаблон 9955XXXXXXXX.