Pessoal preciso de uma ajuda pra resolver isso!!!

Tenho um cenário de testes com Elastix 2.3 + A2biling + dois ramais configurados,
estão fazendo ligações externas e tarifação normalmente, porém não faz ligações entre os ramais.
Já tentei algumas dicas que achei pela internet mais não deram certo.

Vejam os logs de uma tentativa de ligação do ramal 4000 para o ramal 4001;

== Using SIP RTP TOS bits 184
== Using SIP RTP CoS mark 5
-- Executing [[email protected]_callingcard:1] Answer("SIP/4000-00000017", "") in new stack
-- Executing [[email protected]_callingcard:2] DeadAGI("SIP/4000-00000017", "a2billing.php,1") in new stack
-- Launched AGI Script /var/lib/asterisk/agi-bin/a2billing.php
<SIP/4000-00000017>AGI Tx >> agi_request: a2billing.php
<SIP/4000-00000017>AGI Tx >> agi_channel: SIP/4000-00000017
<SIP/4000-00000017>AGI Tx >> agi_language: pt_br
<SIP/4000-00000017>AGI Tx >> agi_type: SIP
<SIP/4000-00000017>AGI Tx >> agi_uniqueid: 1398617452.23
<SIP/4000-00000017>AGI Tx >> agi_version: 1.8.11.0
<SIP/4000-00000017>AGI Tx >> agi_callerid: 4000
<SIP/4000-00000017>AGI Tx >> agi_calleridname: device
<SIP/4000-00000017>AGI Tx >> agi_callingpres: 0
<SIP/4000-00000017>AGI Tx >> agi_callingani2: 0
<SIP/4000-00000017>AGI Tx >> agi_callington: 0
<SIP/4000-00000017>AGI Tx >> agi_callingtns: 0
<SIP/4000-00000017>AGI Tx >> agi_dnid: 4001
<SIP/4000-00000017>AGI Tx >> agi_rdnis: unknown
<SIP/4000-00000017>AGI Tx >> agi_context: a2billing_callingcard
<SIP/4000-00000017>AGI Tx >> agi_extension: 4001
<SIP/4000-00000017>AGI Tx >> agi_priority: 2
<SIP/4000-00000017>AGI Tx >> agi_enhanced: 0.0
<SIP/4000-00000017>AGI Tx >> agi_accountcode: 0962140884
<SIP/4000-00000017>AGI Tx >> agi_threadid: -1226884208
<SIP/4000-00000017>AGI Tx >> agi_arg_1: 1
<SIP/4000-00000017>AGI Tx >>
<SIP/4000-00000017>AGI Rx << GET VARIABLE IDCONF
<SIP/4000-00000017>AGI Tx >> 200 result=0
<SIP/4000-00000017>AGI Rx << ANSWER
<SIP/4000-00000017>AGI Tx >> 200 result=0
<SIP/4000-00000017>AGI Rx << SET VARIABLE CHANNEL(language) "br"
<SIP/4000-00000017>AGI Tx >> 200 result=1
<SIP/4000-00000017>AGI Rx << SET CALLERID 4000
<SIP/4000-00000017>AGI Tx >> 200 result=1
<SIP/4000-00000017>AGI Rx << CHANNEL STATUS SIP/4000-00000017
<SIP/4000-00000017>AGI Tx >> 200 result=6
<SIP/4000-00000017>AGI Rx << EXEC DIAL SIP/VoipRaiderT/00554001,60,HRrL(11977000:61000:30000)
-- AGI Script Executing Application: (DIAL) Options: (SIP/VoipRaiderT/00554001,60,HRrL(11977000:61000:30000))
== Using SIP RTP TOS bits 184
== Using SIP RTP CoS mark 5
-- Called SIP/VoipRaiderT/00554001
-- SIP/VoipRaiderT-00000018 is making progress passing it to SIP/4000-00000017
== Everyone is busy/congested at this time (1:0/1/0)
<SIP/4000-00000017>AGI Tx >> 200 result=0
<SIP/4000-00000017>AGI Rx << GET VARIABLE ANSWEREDTIME
<SIP/4000-00000017>AGI Tx >> 200 result=1 ()
<SIP/4000-00000017>AGI Rx << GET VARIABLE DIALSTATUS
<SIP/4000-00000017>AGI Tx >> 200 result=1 (CONGESTION)
<SIP/4000-00000017>AGI Rx << STREAM FILE prepaid-dest-unreachable "#" 0
-- Playing 'prepaid-dest-unreachable' (escape_digits=#) (sample_offset 0)
<SIP/4000-00000017>AGI Tx >> 200 result=-1 endpos=11040
<SIP/4000-00000017>AGI Rx << CHANNEL STATUS SIP/4000-00000017
<SIP/4000-00000017>AGI Tx >> 511 Command Not Permitted on a dead channel
-- <SIP/4000-00000017>AGI Script a2billing.php completed, returning 4
== Spawn extension (a2billing_callingcard, 4001, 2) exited non-zero on 'SIP/4000-00000017'