Outgoing calls

Hi,

I configured 1 SIP phone as an agent but I am NOT able to call out. This is what i see at CLI…

-- Executing Dial("SIP/300-b7c00520", "ZAP/g0/0121111|20") in new stack
    -- Requested transfer capability: 0x00 - SPEECH
    -- Called g0/0121111
    -- Zap/1-1 is proceeding passing it to SIP/300-b7c00520
    -- Channel 0/1, span 1 got hangup request
    -- Hungup 'Zap/1-1'
  == Everyone is busy/congested at this time (1:0/0/1)
    -- Executing Hangup("SIP/300-b7c00520", "") in new stack
  == Spawn extension (incoming, 90121111, 3) exited non-zero on 'SIP/300-b7c00520'

But, if i called out from another SIP phone which is not an Agent… I have NO problem …

   -- Executing Dial("SIP/200-b7c00520", "ZAP/g0/0121111|20") in new stack
    -- Requested transfer capability: 0x00 - SPEECH
    -- Called g0/0121111
    -- Zap/1-1 is proceeding passing it to SIP/200-b7c00520
    -- Zap/1-1 is ringing
    -- Hungup 'Zap/1-1'
  == Spawn extension (incoming, 90121111, 1) exited non-zero on 'SIP/200-b7c00520'
    -- Hungup 'SIP/200-b7c00520'

Any idea what I have to do?

Thanks… and appreciate…