When i use HylaFAX Client on my Desctop to send fax i see for example something like this on CLI:
  -- Accepting AUTHENTICATED call from 127.0.0.1:
       > requested format = slin,
       > requested prefs = (),
       > actual format = ulaw,
       > host prefs = (ulaw|alaw|gsm),
       > priority = mine
    -- Executing [90048XXXXXXXXX@from-internal:1] Macro("IAX2/81148-46", "dialout-trunk|1|0048XXXXXXXXX||") in new stack
And we see he use "IAX2/81148-46" user to send fax. But on print port configuration i set 81058 user. 

So i try many time to send fax always use user 81058 but asterisk use always different "IAX2/xxxxx-xx" to send fax.

how can i debug communication between Hylafax and asterisk and check why he use random user for sending fax.