Tu proveedor te esta rechanzando la llamada:
<--- SIP read from UDP:192.168.3.2:5060 --->
SIP/2.0 403 Unknown User/Endpoint Not Allowed
Via: SIP/2.0/UDP 192.168.3.125:5060;branch=z9hG4bK42483365
From: "619869****" <sip:619869****@192.168.3.2>;tag=as362f9920
To: <sip:870****@192.168.3.2>;tag=aprqrjmtc-2me87e20000c6
Call-ID: 023edcc5582a75434de42a920e1a0702@192.168.3.2
CSeq: 102 INVITE
Content-Length: 0
<------------->
-- Executing [s@macro-dialout-trunk:23] NoOp("SIP/331-0000002f", "Dial failed for some reason with DIALSTATUS = CHANUNAVAIL and HANGUPCAUSE = 21") in new stack
La causa 21 es llamada rechazada. Verifica que tus credenciales sean las correctas y trata de añadir fromuser y fromdomain en tu peer.