Felicitaciones por esta herramienta tan importante para toda la comunidad, les comento acabo de instalar Ubuntu Server ultima version, Asterisk 1.4 y A2Billing 1.4.1, mis cuentas de A2B, registran, el problema que no pueden realizar llamadas, de antemano les agradezco por su ayuda y atencion, copio lo que me aparece en la consolca:

[Nov 21 21:10:25] NOTICE[2038]: chan_sip.c:15935 handle_request_subscribe: Received SIP subscribe for peer without mailbox: 2285749999
-- Executing [7135823128@a2billing:1] Answer("SIP/7135823128-00cadcf0", "") in new stack
-- Executing [7135823128@a2billing:2] Set("SIP/7135823128-00cadcf0", "CHANNEL(language)=es") in new stack
-- Executing [7135823128@a2billing:3] Wait("SIP/7135823128-00cadcf0", "1") in new stack
-- Executing [7135823128@a2billing:4] DeadAGI("SIP/7135823128-00cadcf0", "a2billing.php") in new stack
[Nov 21 21:10:29] WARNING[2435]: res_agi.c:2203 deadagi_exec: Running DeadAGI on a live channel will cause problems, please use AGI
-- Launched AGI Script /var/lib/asterisk/agi-bin/a2billing.php
[Nov 21 21:10:29] WARNING[2435]: file.c:664 ast_openstream_full: File prepaid-enter-dest does not exist in any format
[Nov 21 21:10:29] WARNING[2435]: file.c:972 ast_streamfile: Unable to open prepaid-enter-dest (format 0x8 (alaw)): No such file or directory
[Nov 21 21:10:29] WARNING[2435]: file.c:664 ast_openstream_full: File prepaid-enter-dest does not exist in any format
[Nov 21 21:10:29] WARNING[2435]: file.c:972 ast_streamfile: Unable to open prepaid-enter-dest (format 0x8 (alaw)): No such file or directory
-- AGI Script a2billing.php completed, returning 0