The old context:

...
exten => 415XXX975,2,Answer
exten => 415XXX1975,3,AGI(subscribir-voip.agi)
exten => 415XXX1975,4,Playback(beep)
exten => 415XXX1975,5,Hangup



The new context:

[calltest]

exten => 1,1,NoOp(${call_connect})
exten => 1,2,Hangup


The AGI:

        $AGI->set_context('calltest');
        $AGI->set_extension('1');
        $AGI->set_priority(1);
        $AGI->set_variable('call_connect',$call_connect);


the error:

    -- AGI Script subscribir-voip.agi completed, returning 0
Oct 20 18:08:22 WARNING[1354869680]: pbx.c:1921 ast_pbx_run: Channel 'IAX2/voicepulse-in-01@66.234.228.170:4569/3' sent into invalid extension '1' in context 'calltest', but no invalid handler
    -- Hungup 'IAX2/voicepulse-in-01@66.234.228.170:4569/3'