-- Executing Dial("SIP/4301-08249020", "Unicall/g1/21051300") in new stack
    -- Called g1/21051300
Jul 12 14:28:16 WARNING[870]: chan_unicall.c:2644 handle_uc_event: Unicall/1 event Dialing
Jul 12 14:28:23 WARNING[870]: chan_unicall.c:2644 handle_uc_event: Unicall/1 event Protocol failure
    -- Unicall/1 protocol error. Cause 32769
Jul 12 14:28:23 WARNING[870]: app_dial.c:714 wait_for_answer: Unable to forward voice
    -- Hungup 'UniCall/1-1'
  == Everyone is busy/congested at this time (1:0/0/1)
    -- Executing Goto("SIP/4301-08249020", "1-CHANUNAVAIL|1") in new stack
    -- Goto (4301,1-CHANUNAVAIL,1)
    -- Executing PlayTones("SIP/4301-08249020", "congestion") in new stack
    -- Executing Hangup("SIP/4301-08249020", "") in new stack
  == Spawn extension (4301, 1-CHANUNAVAIL, 2) exited non-zero on 'SIP/4301-08249020'